actually, mito, i currently use Maxthon (formerly MyIE2). I have used opera several times in the past, and have always found it quite innovative, if not perfect. afaik it was the first tabbed browser, and has always had robust bookmark options. all of my favorite features from maxthon and firefox are lifted from opera (i mean conceptually; it's not stolen code, i'm sure), like tabs, integrated search, RSS, news, irc, and popup blocking, per-page cookie rules, launch groups, superior bookmark management, and importation of IE favorites. How all of these functions work, however, is different in each program. it's something of a matter of pick-which-bugs-annoy-you-least. In my experience, all of them are less stable than vanilla IE, but all of them are more stable than 200 concurrent instances of vanilla (or even 20). since I have begun using tabbed browsers i have gradually ramped up to where my browser typically has 250+ tabs open at once, so.... ^^;; i admit; i'm lazy; instead of reading things i just leave them open "in case i get to them later". sorry for the copout, but i just haven't used the latest version of opera so "my experience" is that it was incredibly rich but buggy.
my loose rankings (best to worst, haven't used the latest versions of every program):
features/plugins: firefox, opera, avantbrowser, maxthon
stability/compatibility: maxthon, avantbrowser, opera, firefox
render speed: maxthon, opera, firefox, avantbrowser
i'm thinking of giving firefox another try soon, so that the pages i hit will see the need for proper standards compliance, but my g/f is having issues with the latest release of firefox so i might wait till the next fix.