I'm still using .480...love it. Solid. I tried the first 500-series build and it was awful (forget the number...) and someone had suggested that all the 500-series were bad, so I thought I'd wait it out until 6.0.6xx came out...but I'm hearing good things about .570, so maybe I'll try.
Agreed. .570 is stable, everything works well with no issues, and battery life is as good (for me) as any other. I also find the PlayBook Bridge functions to work better with this release.
Most releases from .448 and after are better than .246; but you may as well go with the latest and greatest.
I'd have to agree with pretty much everyone else on this one with .570 being the best. Although it could be different on your phone, I doubt it will be since I've only seen good things about .570. The only bug I've seen on that OS is after a reboot, when you go to your applications screen it's blank, but you exit out and go back in and it's normal again.