I played Rush poker once or twice back in the days before Black Friday. I have never bothered to try any of the other sites versions of it, since I didn't really care for it all that much. I know a lot of players like it because of the speed and the number of hands you get to see. I prefer to watch the action at the table and look for patterns and variations in my opponents play that I can then take advantage of.
I never really cared much for RUSH either. I have given some of these others a go though (SPEED on iPOker, SNAP on 888Poker, & ZOOM on Stars) and have found it to be pretty addicting.
If you play enough hands of it you will get to recognize who all the regulars are pretty quickly (also, checking to see which ones are playing max. number of tables is a bit of an indicator). I think I played ~75,000 hands last month alone of one form or another of this format.
I've only played a bit of SNAP (cash tables) and only at micro limits. One thing I do not like about it is that you're limited to playing only two tables, another is that it is ALOT slower moving vs. the other sites. The positive side of SNAP is that the players on 888Poker micro tables are a gazillion times worse than the other sites.... it'd be a great place for a newer player hoping to build a small bankroll from a minimal deposit.