I've been using tabmixplus since ~2005, and would just like to say (because I haven't before) that this add-on is the best, by far, of any Firefox add-on I've used.
TMP is the reason I stuck with Firefox through the years when it had become a memory hog. During that time, there were many times that I tried out other browsers (Opera, IE (again), Chrome, Safari, and even lesser known alternatives) because I was very unhappy with how much memory Firefox was using and it's horrible slowness. For awhile Firefox was almost unbearable when once it had been a smooth fast cougar. Without TMP it would have been. I could never switch though because the interface that TMP provided was not something I could replicate in any other browser.
DeepBlueSky is saying exactly the same that i was going to say, so i qoute him instead of making a new thread.
I cant live without TMP, i tried but almost died (my internet experience was grey, grey, grey and so boring) back to FF and TMP, the second after the sun starts to shine again and internet was again internet.
So Thanks a million times for TMP, the only add-on I cant live without