Peter O’Kelly has written an excellent article on the features, strengths and areas of colloboration between Microsoft’s Office and Sharepoint Team Services and Groove.
We use Groove every day pretty extensively and it does a great job for us. We signed up for but subsequently abandoned a Microsoft Sharepoint Team Services site last year — it just didn’t meet our collaboration needs. For us, Groove handles the basics well — with some still very rough edges around the user interface, a need for tighter file system integration, etc. For me personally, my major desire is a Mac Groove client that would at least allow participation in the secure file sharing aspects of Groove.