In this post, Ronan Bradley gives Microsoft props for taking a sensible approach to ESB.  He writes:

"What I found striking was how Microsoft, unlike some of the other major players, seems to understand that SOA requires a different view not only of architecture but also about middleware.  In particular, the “one stack to rule them all” doesn’t hold water.  There will almost always be a need to implement your SOA across multiple infrastructures."

Some of the same themes were echoed here in an Architecture Journal piece last August.  There's more to come from Microsoft on SOA and ESB technology.  We'll let you know as more goes live...

-Keith