@shanselman pointed out an interesting blog post titled "Building a web app the Microsoft way" where the author Jeremy Baines dose a good job of giving the facts that he and his team found while developing ‘Meet with Approval’. I could not find the case study that was mentioned but that is because the case study site sucks, I will try to find it internally and find the external link.
I know that I have tainted opinion but I don't see why more people\companies\startups don't evaluate the MS stack. From all of the comments only one that I saw was accurate and that is that Windows hosting is quite abit more expensive than LAMP hosting but I think that price will be coming down with the new support we have in Windows Server 2008 for hosters. I also think that a company looking at long term success and would want to look at the cost of self hosting, there are a lot of reasons that Windows for self hosting can be more cost effective but the big one for me is support.