I found out the hard way that ATT's newest release for V5 device software, the version that ends in 822, has a major bug that affects many devices. (Phone won't ring). KB24307-Ring tones and alerts do not play regardless of the tune or volume setting
Days spent with RIM tech support trying to figure this out. And it was one of the techs who insisted I update to that version in trying to fix a sync problem. Also the techs did not know that if you're running WIN7, you MUST run version 6.x of Desktop manager. Five won't sync with WIN7/Office 2010. Six works with device software 4.6., which is what I rolled back to get my phone to be a phone again.
Between trying to fix the sync issues, then the dead phone, then a stubborn key store password problem created by all the switching (answer was here in forum, not at RIM tech support, which was clueless on this, despite KB17643), I'm almost ready to go Android or Iphone. Finally, RIM tech support, even at level two, is patient and friendly, but clearly some of those techs were completely unaware of WIN7 issues and the last one I worked with knew nothing about key store passwords.
I've stuck with BB even though my family and most co-workers have gone to the Iphone or Android. I'm at the upgrade point in my contract and honestly don't know whether I'm going to continue with BB.