Trying to load http://test.musicbrainz.org/release/f3c8633b-5de4-424d-8447-fbe9248c5644/edit causes Firefox to max CPU for about 5-10 seconds on my machine (older machine, P4 3.2GHz, XP SP2, FFX 3.5.7). This seems quite slow and resource intensive. My machine and firefox becomes unresponsive during this time.
If I'm loading some other pages at the same time (e.g. at Session Restore) Firefox complains that http://test.musicbrainz.org/static/scripts/MB/html.js:35 has stopped responding and asks me to kill the script. This last part may be a red herring, but worth noting in case it's useful, I figured.