Mozilla has the best tab system I've ever seen with 1.5a. Block popups, javascripts, images, etc based on tab, undo close tab (why the hell they didn't have that before I dunno, but it's certainly a godsend), set label, move tab on tab-bar to left, right, etc etc etc :classic2:
However, Opera is way faster.
I use Mozilla 1.5a and have so many different versions of Mozilla on my hard drive it's skeery. Also have Opera, Lynx, IE, Netscape 4.x and... two versions of Phoenix (now Mozilla Firebird)