Windows on a Mobile Device is not exactly like Windows on a "Smart"phone. The Motorola Q is not like a PC.
Windows Mobile has a long history of instability. Reboots. Rebuilds. Resets. And WM5 is not that much better than PPC. I have a T-Mobile MDA and a Motorola Q. Neither work for me.
The functionality of a BlackBerry for wireless e-mail far exceeds the functionality of any Windows Mobile device. YES, I AM BIASED. Of course I am.
But I also have to watch out for what is out there. I have a Treo 600 (doorstop) and a Treo 650 (doorstop). Now the MDA and the Q. Each and every one has been the BlackBerry killer. My wife had a Treo 650 and traded up to a T-Mobile 7105t. WITHOUT ANY HELP FROM ME
Can you sync your mail to a PPC/WM device. Yes. But unless you have Exchange 2003 with the wireless feature pack, NOTHING is wireless.
BIS is years ahead of what can be done with WM5.
A hosted BES solution could also work for you.