Brilliant
A brilliant improvement from the former game. The better variation on the units is good, but it had been better to make the different factions more playable as a part of the story. So you don't have to backtrack with every race to give them the right upgrades before you can advance the story.
Story is much better, a little repeated at times but it works.
Graphics improved.
The tower could be a little bit less sensitive, it moves in great leaps just by a quick tab on the key.
Unlockables should be more easily available.
Other then the bad stuff, it is really great kept me going for a good while.