From the 'are we there yet?' files:

Firefox 3 Beta 5 is a solid browser, in fact I've been using it as my everyday browser (on Linux) for weeks without issue. That said there is always room for improvement and that's what the new Firefox 3 RC 1 (release candidate) which is now available claims to offer.

RC 1 fixes stability and feature bugs as well as improving performance by fixing even more memory leak issues.

Overall, sure Firefox 3 offers some neat feature improvement and usability upgrades but the bottom line for me (and why I moved to Firefox 3 as soon as I felt it ready) is that Firefox 2 was sucking up waaaaaaaaaaaaay too much memory over the course of my browsing day. If you're like me you keep your browser open all day, with multiple tabs,  among them more than a few sites that are heavy with Ajax. Firefox 2 over time would just eat up memory (and in many cases processor cycles). That just doesn't happen with Firefox 3 (at least in my experience thus far).

There was a time when Beta meant - software that isn't ready for prime time. But thanks to Google's abuse of the term 'Beta', that's not the case anymore. Sure Firefox 3 is officially at RC1 now and sure Mozilla developers (being a cautious bunch of perfectionists) are aiming to further improve stability and performance -- which is all good - but my reality is that Firefox 3 works for me now.

Mozilla will still likely have at least two more release candidates before finally taking Firefox 3 out of the oven. As opposed to the run up to the Firefox 2 in which Microsoft's IE 7 was in a neck and neck race, IE 8 is still an early release that will likely take many more months till it's close to being a viable competitor to Firefox 3.