Protoss
Tempest: The first thing I noticed, when making a Stargate, was that the Carrier was gone, and in it's place was the Tempest. Already, this decision by Blizzard has some major implications. It means that the Tempest is going to fill the role of the bad-ass, nostalgia inducing Carrier. The same Carrier that struck fear into the hearts of every Fastest Map Possible, No Rush 20 player. Taking away the Carrier from Protoss is like taking Siege Tanks from Terran. It's a core unit that people associate with Protoss, even though it might see little play in Starcraft 2.
With all that aside, the Tempest didn't evoke much excitement from me. It's a slow moving, semi-durable air unit that attacks slower than 90% of the units in the game. It's only redeeming quality is it's range, which comes in at a whopping 22. To put that into perspective, a Siege Tank's range is 2-13, but has a sight range of 11. A Siege Tank normally shoots at 11 range when it has nothing spotting for it. If this were to stay in after launch, no Terran would be able to siege up against a Protoss base defended by a handful of Tempests.
Without the range, the Tempest is a unit that would not be worth it's money, or tier investment. With the range, it's insanely abusable. I also don't think that there is a middle ground with this unit. Yeah, Blizzard could tweak the numbers on it's damage, or it's range, but in the end I feel like Carriers are a much more interesting unit, and pay out more for the hefty investment of going tier 3.
Verdict: The Tempest just isn't unique or exciting; Bring back the Carrier.
Mothership Core: When I began playing around with this unit I used the ability Energize. Immediately, I thought of how broken it would be to have constant Chronoboost on your Cybernetics Core, then on your 4 Warp Gates. I didn't work out the timings, but it seems like this could be easily abusable.
Aside from Energize, it's other three spells are Mass Recall, Teleport, and Purify.
One of the more fun spells was Mass Recall. Think Scroll of Town Portal for Starcraft 2. My main use of it during the few games I played was to be super aggressive, maybe take a base or two, then yank all my units out of the grasp of a surround, or protect my base from a counter attack. This spell, in the right hands, can make Protoss insanely powerful.
Normally, Mass Recall is a Tier 3 spell that comes off the Mothership, a unit with a long build time and great cost. Now, Mass Recall comes from a Tier 1 unit that is cheap, easy to build, and costs 0 Psi. This unit will be making an appearance in every single game, meaning Mass Recall will be used more frequently. I feel that for how accessible this spell is it will allow give a lot of bad Protoss players room to screw up. Imagine if I over extend to try and kill a Zerg expansion. I get the hatchery, but my units are now surrounded by Zerglings and Roaches. In Wings of Liberty, with this, I've basically said, “Killing this hatchery is worth me losing these units.” In Heart of the Swarm, I'm saying, “Look at me, I've killed your hatchery with little to no cost.” Maybe it's necessary for Protoss to have more mobility in Heart of the Swarm, considering all the different units and options available to the other races, but for right now, I think it's too strong.
For the other two spells, Teleport and Purify, there seems to be some lack of creativity. Teleport is bland, and unnecessary. At the cost of 100 minerals and 50 gas, the Mothership Core doesn't seem like a high priority unit that needs to protect itself by jumping around from Nexus to Nexus. In conjunction with Purify, I feel like Protoss gets a free Planetary Fortress whenever they choose. Does Protoss really need to have that much defensive power?
You don't usually see Motherships in games. I think they added the Mothership Core in because the Blizzard design team felt that it was too hard to access the Mothership, so they made it almost a staple of the anyone's build.
Verdict: I feel Mass Recall and Energize are too strong for how cheap and low Tier the Mothership Core is. However, Teleport is impractical for how easily you can replace a Mothership Core, and I liked Purify when it was called Planetary Fortress.
Oracle: The possibilities with this unit make it feel like Stargate is the new Robotics Bay. The Oracle can cloak entire armies, produce a long lasting scan of an area, with the only caveat being that it has to be centered on a building, and it can block off worker units from gathering resources.
This unit is pure gold for Protoss. It makes Stargate builds much more viable and brings in new options for Protoss who want to play aggressively.
Verdict: This unit is strong. Maybe too strong. It's got all the tools to reinvent the way Protoss is played, and maybe too many useful combos with other Protoss units.
Recap: Remember, Blizzard has stated multiple times that their goal is to make the races more individual. With the Tempest, Mothership Core, and Oracle, I feel like Protoss is homogenizing slightly with Terran.
Terran
Warhounds: This unit confuses me. Mech play isn't used extensively in Starcraft 2. It's good, it could become the biggest and baddest thing for the game, but we still see people like MarineKing Prime dominating with just Marines, Marauders and Medivacs. They feel too niche to be worth building against organic enemies, and against Terran, people will just counter it with Bio. The only role that this unit will succeed in is against Protoss. So congratulations Blizzard, you've made a unit that's only viable in one match-up.
Verdict: The Warhound's role is too specific and not interesting.
Widow Mines: This unit will change the way people treat Terran, whether they play them, or play against them. Widow Mines will do what Starcraft 2 units don't do very well: control space. They can be used to create chokes, deny expansions, deny flanks, break up balled armies, and grant vision. Those are just some things off the top of my head. I'm sure the pros will use them in a plethora of new and exciting ways.
The most critical use though is their ability to spread up balled armies. This will change the way you move your units around the map when playing against Terran. This unit raises the skill cap of the game. From now on, you need to pay attention to your army when they are moving, no longer can you 1A across the map with your bio ball or Protoss death ball while you go back to your base and macro. Now you need to pay close attention to where you step against a Terran.
Verdict: This is just the thing that Terran needs. It has a multitude of possibilities that I can't wait to see them utilized.
Battle Hellion: OK, so mech isn't seeing too much play, or huge success in the current meta, so what does Blizzard need to do? Change the mech units so they synergize better. With the addition of the Widow Mine, things are going in the right direction. With the addition of the Battle Hellion, things are getting pretty solid. Battle Hellions aren't going to see much play, other than facing Zerg, I'd imagine, but it's not so specific that it can't be viable in all match-ups.
Verdict: Good news for mech users. Bad news for Zealots and Zerglings.
Recap: Terran got a lot of buffs to mech. Blizzard is doing their best to bring mech into competitive play, and for the most part, I approve.
Zerg
Viper: So, Zerg has had the short end of the stick when it comes to powerful casters. They have the Queen, which is awesome, don't get me wrong, but they are very slow, and are practically glued to their hatcheries. Then there is the Infestor, which is a strong tier 2 caster, but falls short in some areas.
All of that is about to change. The Viper is the Tier 3 caster that Zergs have been asking for. With it's ability to yank power units out of death balls, and protect Zerg units with it's Blinding Cloud, it gives Zerg a fighting chance in late game battles that normally they would be forced to go other tech options.
Verdict: Abduct is a new mechanic to Starcraft, and Blinding Cloud is an old one, but I think both work well together for this new unit.
Swarm Host: People asked for the Lurker back, and they got the Swarm Host. Good replacement? Only time will tell, but for now, it definitely fits in with the Zerg arsenal. With it's ability to wall up the front of an attacking Zerg army, and control space, it seems like this is a damn good instrument for Zerg's ground game.
Not only does it fit in strategically, it fits in aesthetically as well. After burrowing these mother truckers and having them launch a few waves of Locusts, along with the normal Zergling/Hydralisk army, I felt like I was legitimately swarming the enemy, a feeling that has been lacking with the current pallet of Zerg units.
Verdict: Swarm Host fits in nicely. It gives more longevity to a Zerg army and it matches the motif of Zerg well.
Ultra Charge/Hydra Speed: These two buffs make Tier 3 worth it for Zerg ground. It's hard to imagine anyone going for Zerg air units anymore with such a solid ground game going for Zerg.
Recap: A lot of Zerg pros have been complaining that the race is weak in later stages of the game, and there's only one viable build for late game, which is going mass Brood Lords. With these recent additions, I can't imagine that these complaints will remain valid.
I'm very excited for the new ingredients being added to this game. Some of the new mixtures probably won't make it to launch, but hopefully, the ones that remain will keep the game fresh until Legacy of the Void.
(edit: Changed the colors to correctly represent the races.)