I've listed the stack of add-on apps that I have on my 650, but I have to say that I have NEVER had it freeze up on me during a call. I'm on Cingular and have used it pretty much from California to Vermont without an issue while I was speaking with someone.

Yes, I've had it reset on me, but that comes from when I try to make the Treo multitask, primarily when I'm using the web, have AIM/YM/MSM all running, then decide to make a call. Honestly, I sort of take the blame for those moments on myself!

The blackberry does seem to be more stable to me. However, until it matches what the 650 can do in a single device, I'll stick with the Treo.