I apologize for being harsh, but there has not been one major justin.tv stream that I have seen that has been enjoyable to watch. Seriously. Last year's startup school, this year's startup school, the wolfram alpha launch. It's either the audio cutting out, the video freezing, or both. I appreciate that the service is free and that they're working hard to get it to work, but honestly, this has happened so many times to the point where I'd just rather read people's summaries of the talks than trying to tolerate the choppy videos anymore. It's gotten a bit ridiculous.
I get they're a YC company, cool, but in following years, you should give an alternative, like UStream, etc, if the quality there is better. I try to avoid justin.tv as much as possible in general now.