The way tabs should be! Rated 5 out of 5 stars
This is now one of my must-have extensions. (It's right up there with Web Developer Toolbar, FireFTP, Firebug and Session Manager!)
I especially like the usefulness of the tree view when I have too many tabs open (which I always seem to do), automatically creating child nodes, the fact that my pinned tabs are above the tree, and the skins. There are a lot of nice options, too.
It's interesting that there's an API. I'm a programmer, so I may look at that, but right now I don't know how I'd use it.
The only problem I've had was that apparently I managed to resize the tree to 0 pixels wide. Then I couldn't grab it to pull it back out. The workaround was simple: I hit F11 to put Firefox in full screen and then I could resize it back to where I really wanted it. I was playing around with sizing and auto-hide, but not sure of the exact steps that caused it. I did try several combinations for the Auto Hide and "Show ... automatically when", but those didn't "return" it.
A suggestion would be to show the favicon.ico for the active tab at full size in the tooltip. Or provide some way to see it full size. I just like to see them at full size so I can appreciate the artist's effort. ;-)
The tips for writing this review say not to call it "Great" or "Bad", so I'll call it "Excellent!" (which is what 5 stars mean, anyway) and, bottom line:
Thanks for a fantastic tab manager!