As of 2010-08-07 it is safe again to update to the chromium nightlies without losing large amounts of functionality. As of chromium-browser 6.0.487.0~svn20100806r55176-0ubuntu1~ucd1~lucid, the issue with <video> and <audio> tags has been fixed, and these pieces of HTML5 are working again. This means that my HTML5 video gallery is working again in chromium, as well as the YouTube HTML5 preview. Hurray!