I enjoyed it alot at first, got bored with it about a week later, then right when I was about to give up I met some cool people to hang out with in the game. So IMO unless you can get into the "social" aspect of the game there isn't much there.
X-Box Live has the best online play in the world. It runs rings around PS2 and even PC games. I have never had problems with Rainbow Six 3. There isn't as many assholes as on the PS2 online. Hardly any cheating.