I have an HTC Pro with ATT. The hardware itself is cool.
However, Windows Mobile is frustratingly slow, disorganized and unreliable.
Press a softkey and you can get GUI feedback that the button was pressed without the OS or app actually taking that action. That's bad enough, but when button presses can take 1 or 2 seconds to execute because of all the bloated WM overhead, then you don't know if you need to press the button again or wait.
If you do press it again and WM was just lagging, then you get two presses. Nice design feature.
WM is designed first as a Microsoft platform, then as a phone. The phone features integration on WM on the HTC Pro is terrible. The phone screens are miserably organized for quick / easy use. The contacts features have inconsistent use of buttons and softkeys. The dial and phone buttons change meaning. Even the volume functions are poorly designed for quick changes. The Touchflow GUI that was poorly integrated on top of WM is pretty - pretty useless. After one or two superfluous menu levels, you end up in the original balky WM GUI, which is what they were trying to cover up anyway.
I haven't loaded any extra apps on it that might destabilize it, but I have to reboot it at least once a week.
Yeah, the HTC Pro with WM is wonderful. <gag>