Not to dissuade, but Split Second isn't getting a lot of multiplayer play online. The single player experince is OK to good, but not consistently great. If you had a group of pals to play with, it would be fun, but if you're buying it for the multiplayer, don't expect a lot of players.
I was really looking forward to Split Second. Played the demo and thought it was great. Me and my pals had nore "Holy !@#" moments then we'd had in a long time. But somehow, it just didn't... get better or something. I know that sounds weird, but it got old.
However Blur, the game I thought would not be as good as Split Second, is fun as hell. It's almost like Demon's Souls in it's unforgiving nature. You can go from 3rd to 10th in the blink of an eye. Getting juggled like your in a fighting game is even more frustrating when you're in a car.
Anyways, my 2 cents. Enjoy!