I've watched both (TO game blacked out here in the US) games on gamecenter and have been pleased with the quality. Ran smooth on both my laptop and desktop in firefox, no crashes (haven't had the need to try IE yet). Only problem I have had was the feed freezing and having to hit the refresh button. It happened twice in the Philly game, no problems with the Buf game.
I like the radio sync and used the CJAD feed both times. Mostly spot on, sometimes a 1-2 sec difference. Much better than listening to the tv commentators here in the states. Other than the obscene amount of blackouts in my area (BOS, NYR, NYI, NJD games), not a bad deal to be able to watch the habs as I have no other option.