For me, I'd like to see Microsoft getting involved in existing Open Source projects rather than reinventing the wheel and then championing these projects. I've been using the Castle Project stack for a number of years now and in my opinion it would have been a breath of fresh air if Microsoft could have joined the Castle team in improving their already stable and mature code-base. Instead they decided to create their own MVC project from scratch. Just imaging the platform us web developers would have had if MS had decided otherwise. I've used ASP.NET MVC, but found that I had to import so much from Castle that I found my self wondering why I just wasn't using MonoRail as well. MonoRail/ASP.NET MVC is just one example, there are many others of course.

I guess the problem is that mainstream developers will only start using something that is part of the official MS product set and MS have business strategy reasons why creating their own products is the only way forward. It's just a shame. Stop reinventing the wheel and start supporting existing projects, that's my thought.