I just noticed a change in the YouTube player when looking at my Get Seen: Web Video session preview on the WordCamp Boston blog.
There's now a menu item in the player menu bar at the bottom of the video that lets you select the resolution you want for playback.
The choices are 360p, 480p and 720p.
This option becomes visible after you press the play button.
BTW, if you wanted to go to WordCamp Boston this weekend, but didn't get a ticket, there are some charity auctions on eBay right now for a few WordCamp Boston VIP tickets.