WAY too hard!
It was pretty difficult in the beginning, had to restart PLENTY of times. Then I got the hang of it and got up to wave (17?), somewhere around there, at least above 15 (it was the Battlecruiser mission). I had the Defiler in the right spot (second from bottom), Queen's nest, upgraded Overmind, and 3 Spores. When the BC finally came, my defiler attacked it and I had my Discharge on that thing until my MP ran out and it still attacked. All the enemies were attacking my base as my defense was down (including Queen) and the BC kept attacking. It's as if that level's impossible or something. It's also VERY hard to level up the Overmind due to gaining experience only from powers and not the defense. I never got the chance to be able to create a Zerg Mound =[. Also, nothing can kill the units that're attacking (close range) except for my powers, which runs out fast and is needed for other units also. Perhaps a defense that can attack close range (sunkens didn't help)? Have you even played the game?
Suggestions:
Easier
Shortcut keys (very hard without them having to click everywhere)
Possibly less lag/smoother gameplay?
More fair for us
Faster MP regeneration
EVERYTHING raise up Overmind EXP (including defense, not just powers)
Close range defense (Sunken Colonies didn't get the units attacking)
That's about all I can think of at the moment, but there are others. This game is fun and addictive, but the unfairness and everything negative stated ruin it. Hope you take my suggestions into consideration. Well yeah, sorry about the long submission =]