Beautiful post by James Robertson on the Whidbey slip: short release cycles improve quality. This has absolutely become the consensus over the past half-decade.
However, the .NET infrastructure significantly affects this particular release: the CLR itself, the compilers, and the major applications (SQL Server, Visual Studio) boot-strapped with those require either a single synchronized release or a series of transitions spread out over months or years (like a long-running transaction in the database world) that would inevitably attract screams of "why is this so complex?"