Have a bit of concern that can be easily addressed by some compare/contrast. Have noticed the framerate compleatly stop for a second or so a few times in the Nightclub. Have watched some Youtube videos that seem to show this is just the game and hence not a crappy disk but could do with more reasurance.
 
Hitches happen when I get down to the lowest level of nightclub (4:48 - 4:52 in the video below though it tends to vary depending on route taken once down there for me) and also during the shooting and fall though window (This is also shown in this video)
http://www.youtube.com/watch?v=NnakRx0Dk9c

I never experienced a hitch when I was just walking around in the nightclub, but I did indeed experience one when the guy fell through the window.

The nightclub level works just fine in single-player. Some of the dam levels had a lot of explosions and men on-screen at once and that did slow the framerate.