I was in the middle of backing up my add-ons and I realized that I've never taken the time to say so but thanks for developing QuickFolders. It's one of my favorite and most used Thunderbird add-ons. You should consider adding a link to this page on your site.
This review is for a previous version of the add-on (0.7).
Along with Quickfile and Nostalgy, I would not be without this extension. I file emails in many folders, including in client folders. For the clients with a lot of email, I put their folder (actually a shortcut) on the QuickFolder bar and can then drag and drop without having to search for the folder. As a clients email volume decreases, I remove that name from the bar.
Another great function is that clicking on a name on the bar takes me to that folder immediately. I also put the Inbox as the first folder on the bar so I can instantly return to the inbox.
One other nice aspect is that I can change (shorten) the name of the folder on the bar even though I wish to leave the actual folder with a longer name.
This review is for a previous version of the add-on (0.3).