As has been pointed out, MS are buying Groove, not Notes. You might as well compare Windows XP with MS-DOS.

I've used Groove since version 1. Now that it's made it to version 3, it's a very nice piece of secure P2P software that really supported team collaboration that I was involved in extremely well.

I've been wondering how MS were going to support secure P2P collaboration in Longhorn. Now I think I have the answer.