Wow. I installed Groove a few days ago on advice from Dennis and tried the File Synchronization feature. There are few things I will say this about. It's Magic. I can just drag stuff to a folder and it replicates to all my machines, w/o the use of a centralized server. Yes, this is basically doing P2P File Sharing from anywhere on the Internet to anywhere on the Internet (running the Groove Software of course). It doesn't get easier than this. The other day I tried to tell my parents how to copy pictures from their laptop to their desktop. They didn't know how, so they literally emailed them to themselves (cause they know how to do that). It didn't work though cause hotmail didn't take their 200 MB of attachments. Ack!
Groove is awesome and I'm at a loss for words. I can now have all my stuff w/o doing the hack of a job I was doing manually dragging folders around using Windows File Sharing (painful).
The Groove feature is a lot like the Castle feature in Longhorn (the file sync aspect of it). I don't even care what else the Groove software does. This feature alone is worth the money. Oh, it also sync's Favorites across all your computers. So long FavoriteSync. Groove even uses less RAM than FavoriteSync.