I've read quite a bit re: the SDL as of late in the universe.
First, we put out this doc which talks about what the SDL is, and how it works.
Then, RHensing tells us what his new gig is, and how it involves the SDL.
And I've since seen a few mentions of it on the blogs.msdn.com and blogs.technet.com homepages.

While I am not knowledgeable enough in such spaces to have opinions worth listening to, the results (like those in the article above re: 2k vs. 2k3) seem encouraging to the casual observer.