Don't get me wrong, I enjoy working with SQL Server, but I think Microsoft has made a strategic mistake with Yukon.

SQL Server needs to support truly Shared Nothing clustering.  In a world where Microsoft is espousing the need for Web Services, where they are pushing for a de-centralization of software from any given computer, to multiple computers at any distance, their database will have to handle the expectations of such a world.

If I try to sell a piece of software that runs on remote servers via a variety of clients in the field (Web, WAP, Winform, etc) then my client will expect, reasonably or not, almost no downtime on the application.  That means my database must be robust enough to handle small hardware problems without stopping.  Oracle has had this going for a while now, you can cluster Oracle servers, and then take just 1 of them off-line to work with, the rest will pick up the load.

We need to get Scale-Out not just Scale-Up for SQL Server, or you're just cruising for problems.