Hello,
I am planning to release version 2.1 next Saturday (a week from now) - the most important change is the addition of a "Recent Folders" Tab, I believe all active Locales (except for hu-HU) have already been updated, thanks to all contributors for their awesome work.
(I have PM'ed the Polish Translator, as it looks like he has given up half-way)

Tip: The "recent folders" label can be hidden by right clicking the "display recent folders tab" option and then toggling extensions.quickfolders.recentfolders.showLabel:

this also has some settings for alphabetical sorting (default is sorted by time stamp) and number of displayed items (12 is default)
Another important bug fix is support for dragging emails from a find results window

, this previously threw an error.
It is likely that this release will not be supporting Thunderbird versions before 3 anymore as it extensively uses the new (Javascript 1.7) "let" keyword, and I haven't found any way to hide this from TB2 so that it renders the whole extension unfunctional :(
But I am glad to say that Postbox and SeaMonkey will support the new feature (this was a fair bit of work as they handle their recent folders differently; this required quite a large amount of hacking but I think the users will be grateful)
Behind the scenes: one user opened a bug about the ugly color choices and is currently working on a better set of colors so this will be in a following release.Hopefully we shall have these for version 2.2