Just joined bwin today and I was very impressed. The livestreaming is awesome because you actually get coverage of the 1st and 2nd courts even in MM tournaments like Kitzbuhel. And it's great to be able to bet on each individual game in a match and loads of other various statistics. Got to be the best bookmaker for tennis I've seen.
But Betfair still has the best odds and the better Live Stream quality for the matches they show (probably not as many as bwin).