I tried it, but I couldn't take to it. It seemed to me like you could play one match and then you've played them all. It has an interesting thing going for it, what with the solid PvP and PvE environment plus the small amount of "skill" players would need to use by retreating from towers and using the minions as a meatshield so you could do damage to the tower and not get owned instantly, and such. Just seemed like it was going to be the same game constantly, with people using their favourite characters and at least one guy per match dominating. It was nice that, generally, deaths don't mean much in the way of winning/losing a match, but obviously if one team is constantly dead then the other team is constantly active and is more likely to win, but yeah.
I tend to shy away from competitive games in general, so that's probably why I couldn't take to it. The different characters and skills were pretty cool though, I quite liked Cho'Gath. The daylight...it burrrrrrrns!