While it appears you've limited yourself to the Treo and the Q, I would urge you to take the BlackBerry 8703e for a spin. While it doesn't have the software available for it that the Treo and Q do, it is a serious email solution, provides decent desktop synchronization, and is a functional phone with very good voice quality.

I gave serious consideration to both the BB and the Treo, but I've heard so many complaints about the Treo's stability that I decided that its other attractions weren't that important. I'm also not crazy about having a touchscreen, or to fumble for the stylus to accomplish many of the basic PDA functions either.

I really shouldn't speak for or against the Q, since I don't have any direct experience with it. Given my experience with a WM5-based device in the Axim X51v, though, I think I'd have to reboot the Q far more often than I'd like.

I've had the BB for 3 weeks now, and haven't had to reset it once.