There are numerous threads about Rush floating around here.
You can get your feet wet for FREE because they have play money rush tables. I highly recommend doing it that way. These games play different (IMO). Ignore the play money part of it and play those just to figure out the mechanics of how these are played.
The RUSH tourneys play different as well. Not sure if they offer play money tourneys yet. I expect they will. Hope to see private rush tourney's as well. IMO Full Tilts solution to make the tourneys work right was brilliant. Once the tourney drops to 3 tables, they don't combine tables as the number of players drops. So with 3 tables left, you will be playing 4,5,6,7,and 8 handed tables. This keeps the flow of the game moving right along. Sort of shoot-outish at that point, but only sort of.
A single rush game will take up the mental capacity (guessing) of maybe 4 tables if you multi-table. Things can move along very quickly, especially if you are folding fast. IMO more hands = better opportunities.
Beware though, if you like these and start playing them, going back to normal tourneys may be painful....... On the other hand, learning to play rush correctly might improve your standard game. Rush can eliminate the patience issues with standard games. When you quick fold, you can see a new hand nearly instantly. So the 'waiting for a great hand' part of it is diminished.
I'm still working on this and am +BR.