Hey gang-- Well, I picked this expansion up last night and have started playing it. It looks very similar to the original game, of course, except that you play a different Marine and there are new weapons (one ripped straight from HL2-that's right...Gravity Gun!!) and several new breeds of demons. Oddly, this expansion is more difficult than the original game. The beasties do more damage and can absorb more damage, and there are fewer health, armor and ammo pickups. Still, for those of you who liked the original creepy Martian fragfest, this one might be worth $25. It also has MULTIPLAYER!!