They are awesome. To me at least, but only if you save space by hiding the regular tab bar and it is easier to manage tabs since they are now closer together. Also, if you make the right --or left, it is up to you, I pick right-- sidebar auto hide and letting just the icons show. You do gain a lot of extra space. Mind you, you need to enable CSS via About:Config. On too of, before, using say, Sideberry. I like you thought I did not like it but now that I have tried it. I simply will not go back. I have a userChrome.css file that place on all my machines on a fresh install, now.