I've just tried it. I think they've got the worst video player in the history of the internet. It adjusts to your bandwidth, but about every two seconds, so it keeps switching between the highest quality and the second highest virtually constantly, and every time it changes it skips and pauses or has to buffer for a few seconds. Worse, it won't let you just manually choose the lower setting and let it buffer for a minute, it doesn't seem to 'cache' at all (is that the word??).
I gave up after a couple of minutes. Absolutely fucking useless.