It looks like Microsoft rolled out the Spring Update 07 early to a few people, specifically all Xbox MVPs are helping to beta test the dashboard update.

Godfree reports that while the new friend features doesn't let you increase your 100 limit for your GamerTag Friends List, it does let you add an additional 600 MSN Contacts to your list, merging the two into one mammoth list. Brian Crecente

I Just Got the New Dashboard Update! [Gamer Tag Radio]