Outstanding even with current bugs... Rated 4 out of 5 stars
VertTabbar is a Great extension!!!
Sadly, development for the extension called Vertigo-( https://addons.mozilla.org/en-US/firefox/addon/1343 ) which was previously my favorite, has died and I've finally given up all hope of resurrection by the original developer who seems to have disappeared and no longer responds. That said, VertTabbar is an excellent replacement in the same vein; simple and efficient! Tree-type tab extensions and the like are flat useless, take up valuable screen real-estate as well as resources, leak, and... NONE OF THEM "EVER" WORKED RIGHT -(if at all!)- on several machines and multiple OS's I tried them on. Along comes ...(or should I say "I found") VertTabbar and hope is once again renewed for a simple replacement/augmentation to the standard horizontal Ff tab-bar!! Relative too the TMP extension, I don't have the same problem color-coding / highlighting the tab text etc. via TMP as another reviewer commented; works perfectly! I do however have a problem each time I change a tab related setting in TMP which causes VertTabbar to jump from the right side of the browser window too the left. I also have All-In-One_Sidebar installed and VertTabbar jumps/sticks to the right edge of it when this jump occurs, not the window boarder. The fix is to open VertTabbar's settings and click the left, then the right radial button to force VertTabbar back to the right side; where it stays unless and until I change a tab related setting again in TMP. When starting Ff, VertTabbar starts on the left of screen, then jumps to the right while loading btw: interesting oddity IMO. Vertigo was on the right each and ever time at start-up without fail for me.
The other issue I have is the inability to scroll or access the hidden tabs-(beyond 23 tabs in my case @ 1024x768 resolution on my main machine). My work-around is the extension called SwiftTabs-( https://addons.mozilla.org/en-US/firefox/addon/380 ), ...but still it's a PIA time-wise having to go through 10-15 tabs individually before locating the one I want, then back again... etc. etc. etc. . Julien, maybe you could look at the source code for Vertigo and come up with some ideas to resolve these issues. Vertigo did function very well with TMP with exception to the auto-hide feature; it worked...sometimes, but would reset to the default width rather than maintain the width I had chosen). I'd give you 5 stars, but until these issues are resolved I must be honest and fair at the same time. I'll continue using VertTabbar because there's no competition for the simplicity it offers. I hope these issues get fixed asap, then, 5 stars it will be! If you request Julien, I'll email my Ff Info listing of extensions, themes, and plug-ins to help you resolve things. Thanks for your time and effort on this one Julien! OUTSTANDING!!! Keep at it please and don't let this one die!