F:NV had framerate issues for me before I even started any DLC, it's just an awful port, but it's the only one I have.

I can look through the fllaws, though it's really making me wish I still had a working JTAG 360. Might have to get one of mine reballed so I can play Elder Scrolls/Fallout games without having them be a
completely buggy mess.
Yeah DMC2 was a lot of fun, it was actually the only one I finished. I played a decent amount of 3, and a little bit of 4, but I just couldn't get into it for some reason. I guess I just probably moved on to a different type of game, I do that usually. I should pick up the HD collection sometime and go through them. Have you played Bayonetta? I love it, it's somehow even more over the top than DMC. I got hooked when I was playing it back on 360, and recently got it for PS3, so I think I might give that one a go here soon. Or maybe just wait to pick up the second one for the WiiU. Since it also has the first one bundled with it.
Haha, yeah the enemies are pretty aware of their surroundings. If you treat it as more of a stealth game, rather than a survival horror, you'll do fine. Though it does get pretty crazy when you're forced to fight, and not just stealth kill everything. About how far did you get in the game?