I am a BIG WM user since inception. I have always enjoyed some of its features and definately its customization. The processors didn't catch up with the OS experience( in truth the WM OS needed a lot of tweaking ) but now with the newer processors the experience is much better but still not good enough for me to look back. I made the move the Android and will consider WP7 when it comes out. I live in and out of Routers and Windows Environments.
Exchange works great and I have moved a large group of clients over to the HTC Incredible and another group this week. They wanted the Apple IPHONE but without the potential of having an extra battery to carry around they had a problem with that. That was their decision not mine as I don't care either way as long as they pay me
They like the Exchange Sync and so do I. Is it perfect? No but it does work well. There are many ways to secure an Android to MS Exchange experience. They tested out the phones for 30 days and are more than happy to make the switch.
You won't regret it and if you do then you can always get the HD2 or HD2 T9193 that will support AT&T 3G.
Good luck and happy Androiding