[psyct1]

I have been on AT&T since 2005, so I have no info on switching from VZW to AT&T however, I did just get the 8310 (had the 8300)...

From what I can tell so far, the 8310 seems to be much more stable (less hourglass appearance) than the 8300.

The GPS on the phone works great, be forewarned though, if you are indoors it is likely you will never connect to any satellites, best thing to do (which I got from here) is to go outside, clear view of the sky, and go to Options>Advanced Options->GPS then click the BB button and click Refresh GPS... the first time you do this it could take up to a minute but, if in a decent area, it shouldn't take much longer than 15 seconds...

I know it wasn't too informative but, hope it helps...