I'm also returning the 8525 today for the Treo750. I've been a loyal Treo user since the days of the Handspring PDA and most recently had the T650.
My new job required that I have a WM phone to be able to easily sync with the existing exchange server, so I upgraded to the 8525 thinking that it was more durable and powerful.
Not so. Frequent call drops and lack of ability to dial phone with one hand (slide-out keyboard is a user nightmare) are my biggest gripes. I also had a terrible problem with the memory card getting stuck. (See the
Cingular forums for more info about that. It wasn't an isolated incident.)
I'm hoping that the Treo lives up to my expectations.