I very much recommend this game for anyone who:
a) Likes tense, realistic zombie games;
b) Wants a game that feels more like a movie (i.e. Dawn of the Dead) than dynasty warriors (i.e. Dead Rising);
c) Doesn't mind a game being unpolished (e.g. currently no NPCs in the build I am playing).
The game is extremely compelling, even if a little thin on the ground for content. You must grit your teeth and carve out some space for your character to call 'home'. Barricade the doors, shut the curtains, create a sheet rope to access the second floor window. Then get building your perimeter wall and planting your crops. Don't forget rain collectors. Now you have the basics of survival, you can make forays into the dangers of the city, staying in cleared out houses along the way and making sure to attract as little attention as possible.
This game has the potential to leave a huge, huge indent on future zombie games, probably the same way DayZ has already done. When NPCs and multiplayer are added (especially LAN which would be incredible), this could become the FTL of the zombie genre.
Considering I have got 30 hours of fun from this game, I would say that it's definitely worth £5. In terms of £10, it's your choice: either wait until the game is a little more advanced and REALLY get your value, or jump in and support the developers early on and enjoy running around a town full of 4500 zombies with no NPCs.
Right now I would rate this game a compelling 7/10 but it has the potential to hit 9 or 10/10.
For reference here is how I rate other non-arcade zombie games:
Resident Evil 4: 9/10
TellTale Games The Walking Dead: 8.5/10
Left 4 Dead: 8.5/10
Resident Evil 2 or 1: 8.5/10
Left 4 Dead 2: 7.5/10
Dead Island: 7/10
Dead Rising: 7/10
The Last of Us: 7/10
DayZ (currently): 6/10 (with the potential to be much higher)
Dead Rising 2: 5/10
As you can see I have left a space at the top for 9.5 and 10/10. Reason being there has never actually been a zombie game that lives up to the tension, excitement and cloying exigency for survival that permeates the finest zombie movies.
Project Zomboid does have a chance to reach that level or somewhere near it. The fact that the merest scratch can but not necessarily will turn you eventually into a zombie is a welcome change to the superhero melee murder spree that many other zombie games offer. The fact that you can die of hunger, thirst, regular disease and being soaked to the bone by freezing rain adds tension. Your crops can die of diseases, a horde of zombies can shamble up to your safehouse and lay siege to it. Firing your gun attracts three times as many zombies as you originally intended to engage.
So there you have my take on this charming, albeit incomplete, little game.