Madison is shipping to TAP customers
They call it their new, massively scalable data warehousing solution; they say it can load 1TB per hour and support data warehouses in the petabyte range, all on commodity hardware. Bold claims, for sure, and I bet you're thinking, "I'll believe it when I see it."
If you can get on Microsoft's TAP list (TAP = Technical Adoption Program) and meet other undisclosed criteria, you can see it now. Otherwise, you'll have to wait until 2010H1. For more details, see: