I won't get into my anti-MS rant (!!!), but it is true that more coders are familiar with CGI than with ASP because it's more common and works cross-platform. I have also heard that MS changes their API often; don't know personally if that's true although it certainly is true in their file formats. I have also heard that lots of .NET is vaporware; YMMV.

One BIG advantage of the open source community is that there are people (like PM) all over the world who are willing to share free support with you. In my book, that blows MS proprietaryware absolutely out of the ocean, no matter how good its purported features may be.