MobileTechReview has a fine review of the Cingular 8525 (aka the HTC TyTN). The device is basically an upgrade from the 8125, but it's an upgrade all around:

The faster processor, HSDPA 3G radio, better camera and Bluetooth 2.0 make it a worthy sucessor to the Cingular 8125 and company, though only you can decide if the price difference is worth it.

Cingular 8525 and HTC TyTN - Windows Mobile PDA Phone and Smartphone Reviews by Mobile Tech Review