I downgraded to .570 (it is actually an official release of AVEA Turkey) from .576 a couple of weeks ago because it was freezing in poor signal areas while seemingly devoting all resources to try and get a good connection. Had a similar freeze this morning while e-mailing on .570, although it seems much less frequent than .576.
I see that .600 is available as a beta and have downloaded it, but will wait before installing to see if .600 has any obvious glitches.