CoDe Magazine has published a rather large article about XNA games development, with a lot of input from professional developers like Jamie Fristrom and Raph Koster (both linked in the left sidebar). There’s a lot of repetition, but it does bring home the point that XNA and C# can be useful even for professional developers today, and will most certainly become more useful in the future. I have only done a couple of minor experiments with XNA 1.0, but I know a few other developers who use it regularly for prototyping or testing ideas.

The biggest problem? Microsoft only; no support for Sony or Nintendo platforms.