Yeah, I read about this before I had even dled Win 7 beta, and honestly was a little put off/discouraged to try the beta. But the curiosity got the better of me. Heck, I said to myself, they've got a fix for the problem--for both the 32 bit and the 64 bit versions, so it won't hurt me much, if I try the beta. And what has REALLY made the difference is that if your mp3 files or folders containing these mp3 files are marked READ ONLY, this bug WON'T hurt them or you. And all my mp3 files--folders containing them are marked READ ONLY; I checked.
At this point, I still have not yet set up Windows Media Player or played any MP3 files or checked my mp3 files, so I don't know if any of them is hurt/ruined. But I had IMMEDIATELY installed the hotfix after I had installed Win 7 beta.
One thing that ticked me off is that I am unable to launch Google Earth(latest version, of course) in Win 7 beta. It hangs at loading with the message of "loading myplaces, kml..." etc. Googled; it turns out that a boatload of people have had this problem--although not within Win 7. Tried the suggested solutions, but no go. I think this might be a bug within Google Earth rather than Win 7 beta, although I had never encountered this problem when I ran Google Earth within Vista. The last part is unrelated to the MP3 bug.