I'm happy everything is working for you.
Regarding the note abouut directshow filter, I do mention that I use 3ivx to enable WMP10 to recognize and play AAC files. I could probably write a longer description about getting everything setup now things seem stable.
In the readme it does describe what is included in the sync "all" option. Having the cover sync seperate is just personally convenient...
I would have to go and check the API's to see what exactly gets modified in the file. It is something roughly like this:
Syncing to iTunes: Pretty much everything except ratings get set in the file itself (hence the iTunes rating export/import)
Syncing to WMP: For AAC files nothing will be updated to the file itself. For MP3 files, most fields will be updated in the file itself (I believe)
Basically if you are confident in your data, you can go ahead and make the changes (I do), if you have a backup you can always go back.
Thank you for your generous offer of a donation, but it is really not needed. I wrote MusicBridge to deal with my own sync issues and figured it might be useful for others. I'm happy it works for you.