Twitch never streams without buffering for me, never has on any ISP, and I mean heavy buffering. No issues with other streaming on Crystal.
Whenever overseas friends send me Twitch streams I just try it out of politeness, but I know it won't work, and indeed it doesn't.
Busy testing here and http://www.twitch.tv/leveluplive for example is fine. Demands around 600KB/s on high as it spikes on occasion though...