IMO we need few things to improve it:
-Have acces through a panel control to old mutation to be able to try it again anytime. (or in case you missed it)
-More maps from blizzard or the community.
Somehow I would like to be able to see some 1 vs 1 with commander, that would give a warcraft hero style into SC2 and it feels like it would be nice. (indeed might be almost impossible to balance but still.)