>But breaking backwards compatibility is just not something customers will put up with.

There's no reason to believe this to be an immutable law going forward for much longer. With more and more going into the browser & cloud, how much is really left on the client side to be backwards compatable with these days?

The first thing I do when I reformat is install chrome, login, and sync my Google Account. I have all my important documents on Google Drive, a full office suite in Google Docs, all my bookmarks, account logins, etc.