I'm only on the 3rd mission, but this game kicks ass! That 2nd mission was awesome.
I will say that you definitely need a power video card to really run this. I've got a GeForce 3 and had to overclock it to run smoothly at 1024x768 in 16-bit color!
So far, it seems like there's some kinda boss near the end of the level, but I haven't played the game very long either.

The wait was worth it thus far!