Go download it now–the folks at Mozilla are also looking to set a new record for downloads on a single day.
I have been using Firefox 3.0 since I think the 2nd beta. I have been happy with the performance and stability starting even then. The three release candidates, in particular, have been pretty much ready for prime time as far as I am concerned.
My critical extensions, like Sxipper, have worked throughout and with later releases, extension support has caught up quickly. With the official release, I expect any actively maintained extensions to catch up soon.
No excuses–download today!