Give it a chance, you might like it..
The way it works is you play with all four instruments (bass, vocals, drums and guitar) at the same time, playing small segments of the song on each instrument in order to keep it going on it's own. So you have to keep changing between instruments while you play the song, and trying not to miss any notes. If you do miss any, you lose the segment you are playing, and have to play the next one in order to get the instrument going again. It's a pretty interesting twist, and gives the game a totally different feel.
This game is not as hard as other rock band games either, you will find that even at expert level it takes very little time to keep getting 100% on every song. The system of touring is the same one as in rock band 2 though. All the gigs seem to have been taken straight from there, with only some songs being different. Overall the whole gameplay and feel of this game are very good. It's what you'd expect from a portable rythm game.
The set list is not that good though.. but i guess that's a matter of taste..
There's really not much else to say.. but i do recommend renting it before buying, because some people will love it and some people will hate it. Give it a try..