Not everyone is (still) impressed with MS's "we're doing open source now too!" initiative (Shared Source I believe it was called). Microsoft's Open Source Trashware is an article where a few of the open source MS projects are looked at. As you can tell by the title, the author is not impressed.
It does seem that the staying power of MS's initiatives falls off rapidly as the marketing campaign ends. Who has heard about the Zune (outside the zune specific blogs I suppose) in the last couple of months? The Vista Ultimate site remained silent for months after Vista's launch, and was only updated after 5 months because of pressure from the internet community bitching that the extras they were supposed to receive after paying the ultimate price for vista were a) lame and b) not updated. Even now, 2 months after the update (which really just said they were going to release more stuff "over the next couple of years") nothings been put on the site.
Of course this (the lack of MS open source projects) may simply be due to pressure at work. We all know how easy it is to be busy enough to really have no desire to do anything in the evening after work, maybe that's the case for these folks? Or they have realized that OSS won't make them money, while working for The Man at MS will.