There was a fleeting moment of consternation in the run-up to the Windows 7 beta as it was rumored to lack support for Windows Mobile. The definitive answer: Fugetaboutit.
Speaking as a longtime Windows XP user who had avoided Vista at all costs, I've had nary a problem using Windows 7 with my Motorola Q9h, though I did have to download Microsoft's Windows Mobile Device Center -- aka WMDC (for you anti-Vista folks, that's basically Activesync with a nice UI on the front end). Hopefully we'll see WMDC built in to the final release of W7. For now, you can get it here.
If you're already used to WMDC, you should have no problems in Windows 7. If you're still looking to get in on the beta program, go download it here (at least through Feb. 10, when the official download ends).
Granted, we were hoping for a little more functionality with Windows 7 and Windows Mobile — Microsoft has this whole darn ecosystem it's working on, it'd just be nice if we could do more than simple sync, install, and file transfer. But, hey: working's working, at it appears to be a step up over ActiveSync.