Went to Silva - Franklin I...also went to Rampage - Liddell, both at the MGM in Vegas.
Both were live as fuck, the crowds are energetic, and the atmosphere is electric.
Suprisingly, there are about as many young women as there are men, well...at least when I've went. Both times, Vegas was crackin as fuck for the whole weekend !
I would definitely recommend going to a UFC event. I've been to two recent boxing megafights...De La Hoya - Pacquiao, and Pacquiao - Hatton, and as far as the atmosphere goes, the UFC events are much more lively, mostly because in boxing megafights a lot of the crowd consist of star gazers, and not hardcore fans.