Assault Heroes takes a stride forward in level design and length, but it's way too dark and a few levels pinch the fun.
Assault Heroes 2 gives you more of the same.... mostly. There's the obligatory new weapons, which, while still fun, are hit or miss. There are also new vehicles to get in, but they're so underwhelming that I found myself opting to play the game through in the default Warthog-lookalike or even on foot instead.
The big plus is that the game is longer -- MUCH longer. It's at least twice as long as the original, so it's hard for me to argue that you aren't getting your money's worth with the game. And since the foundation for the game is so rock-solid, it's even harder to not like AH2.
The game makes two very bad missteps, though. First, the game is way, way, WAY too dark. On my Samsung LCD, I had to crank the brightness from 65 all the way up to 90 to even remotely make the game playable. It's possible that plasmas and CRTs may not have this problem, but since the majority of HD sets being sold are LCD, it's best that you know this before jumping in.
Also, there are a few spaceship levels that are so bad and so poorly implemented that you'll feel as if you've accidentally booted up a different game. These levels are so bad and so floaty, that your opinion on the game (whatever it is) is likely to drop a pitch or two.
Aside from these awful additions (especially the darkness level, which hurts the game tremendously), this is probably one of the finest shooters ten bucks can buy. Hopefully they'll patch it so it isn't so hard to see, because a shooter that you can't see is broken. Were it not for the overall quality of the rest of the game and the fact that brightness can be adjusted, I'd have scored this several points lower.