Eh, don't get too ahead of yourselves, Firefoxmyths is a bit difficult to justify as evidence of Firefox's failures as he kinda overdoes things at times.
Firefox will fare much better than IE in CSS stress tests and certain other areas (maybe resize performance), but there are other measures of speed that make Firefox seem kinda slow. IE rapes Firefox in loading time, for example, as well as UI responsiveness, and up until 1.5 back\forward capabilities. Little things like that.
>>24
Opera 8 was supposed to fix a lot of that and mostly did. The only shortcut I hear complained about anymore is Ctrl-H, and while the panels default to that stupid two-segment mode, the rest of the UI is pretty damn simple and is less obtrusive than Firefox's.
As for it not working well with websites, I cannot say I've experienced this in a negative way, though obviously we might visit different websites. I'd urge you to give it another shot if you're basing your assumptions on a past version, because I don't believe any of these are significant problems anymore.
I also feel Opera is very "stable" and "reliable" - Firefox feels otherwise for me. I think that perception tends to be based on what you're used to, so don't take much notice as you'd probably change your mind if you made Opera your default.