Vegas was pretty good. I liked the cover system, though I still liked Rainbow Six 3's tactical system. You needed so much planning if you wanted to get it right.
Fun to play, though I wasn't a big fan of the PC version's glitches...it happened to Splinter Cell: Double Agent for the PC as well. Both of the ports were horribly done so they had so many glitches and framerate problems when they first came out. I remember the demo crashed even on the lowest settings when I tried it.