I bought this at launch and I just can't get into it like I could Insect Armageddon. The the flying class and the heavy armor class are set up a lot differently than in IA and IMO changed for the worse. I keep trying to play them the way I did in IA, which you obviously can't, and end up getting aggravated as hell and going back to the standard soldier class.
The heavy armor class moves so friggin' slow and those melee weapons and other new additions just aren't as fun to play with as the version in IA which was much more mobile and had a better selection of guns.
Maybe I just haven't unlocked the right weapons to enjoy those two classes with.