This past weekend I finally upgraded my laptop from Windows 7 release candidate (build 7100) to the letterbox version (ultimate). Somehow I manage to find an excuse to reload my operating system every 6 months or so, so I have the pattern down pat. Image the hard disk, write down all my installed apps, copy over the data folders, export bookmarks, e-mail settings and rules, etc. Then wipe the drive and install clean. I will say that the Windows 7 install process was probably the most smooth I've had to date. I was reinstalled and fully patched within an hour, taking only another two to reload my apps and copy over data.
The only hitch was on Outlook 2007, which I use with my GMail account. It installed fine. I changed the data file over to my backed up copy and all my e-mail was fine. But for some reason, every time I would connect to GMail and download, it would download two copies. Reading online I found posts that suggested you check the box to leave mail on the server, which was already the case. I deleted my GMail account and recreated it in Outlook, still nothing.
Then I noticed something... it wasn't downloading e-mail for every folder, just the ones with rules on them. Bingo!
Sure enough, as part of my restore process I reimported my Outlook rules for moving things to various folders. That, it turns out, is now unnecessary. In prior versions of Outlook (and possibly pre SP2) the rules were stored as part of the application and didn't carry over with the data file. That's no longer the case; your rules are now stored in the data file and backed up when you back e-mail up. Kinda cool. So once I removed the duplicate rules everything started working as expected.