Just got an update on Aurora (it's like daily builds of the latest mozilla - with all the nice updates). I've been running it since they made it available and I have not had any issues with it. The only slightly annoying is that almost daily (if you restart the web browser) you have to update it - which on Windows 7 gives you the "can I get elevated permission" dialogue if you have UAC activated. Not so much of an issue but that's it. Also my plugins work (noscript, adblock+ & webmail notifier).
This new version 7 is supposed to have improved memory usage - NICE.
** Update: the new version is noticeably faster than Aurora 6. I like.