Web 2.0!!
Some nitpicking from me:
- loading.gif in jquery lightbox seems to be made for a white version, type in loading gif in google, and there are tons of sites that can generate new ones
. I kind of agree with Phanx about the option to disable lightbox as well.
- You could use jquery history to address previously mentioned problems with the "back" button. http://tkyk.github.com/jquery-history-plugin/
- The screenshots on the addon page could be better. My idea is to enlarge the area for them when you mouse over them, so it will show all screenshots. When you leave the area, the area collapses to 1 screenshot. Easily doable with jQuery I think
Or add a coda slider, whatever 
- When you click the file info button in Firefox, the file info is shifted to the right, also causing an ugly scrollbar(grrr). Add "clear:left" to ".TabTab".
- Facebook like button is cut off on the right.
More to come as I find stuff :P