...and the .aspx
Looking into the Curse change, it's not pretty :(
I think you have to handle new addon ids, even if old URL are redirected.
One simple reason: The regexps can be stored simply in a file external to the program - for all minor changes to the web pages I only have to distribute a new site_re.txt, not package a full WUU installation (which can easily take 40+ minutes if I'm doing a full release on both wuu.vagabonds.info and sourceforge.net, plus updating all forum threads). I'd love to use stuff like BeautifulSoup, but that would require a rather huge change in how the system works.
I understand the your concerns, but xpath are as easy as regexp to store externally and are more powerful to manipulate DOM structures.
Anyway, congrats for WUU which is, in my opinion the best addon updater.