In a recent fit of insanity (and frustration) I decided to apply the modified rom patch to my 6315. This was the best decision that have made since buying this thing!!!! The device is not stable (no resets). The "one ring" problem seems to have disappeared. The bluetooth is so stable that I can go out of range, and when I return the headset is automatically reconnected (never had this happen before). Sound quality is better, and the device seems to run faster. I even reconnected my Jabra BT250 (which previously gave me tons of grief) and it has been working fine. For now, this patch has made the 6315 the device it should have been from day one.
Here is the link:
http://www.lvlolvlo.net/PDA/ROMUpdate.htm
Please read the page carefully before deciding on whether you want to do this. I used the newest patch, which reinstalls all of the tmobile apps. The older update flashed the rom, but leaves the device completely free of the tmobile apps.