We looked into this (me n Jeff) we even brought and xbox 360 to develop on it. I think it might be C#. They have a wonderful website though.
http://creators.xna.com/en-US/The thing that annoyed me with it was that when I was looking into it even though games made with it were testable on PC and XBOX you can only publish to XBOX. I completely understand why they make it that way but still annoying...That being said I've read in other posts that you can publish your game for the PC so clearly something that needs researching some more.
The fact you can only release things on XBOX wasn't the worse thing in the world but when I checked out how popular games were and how much you can charge for them we gave up. The paten was if you didn't charge 20p or some silly amount of money like that, regardless of how sexy the game looked it got no downloads.
There's a massive post here about people whining about sales figures
http://forums.xna.com/forums/t/28043.aspx?PageIndex=1however anything on XBOX would just be a bonus anyway I guess. Whatever we do next Steam is where we want it to be, It's "THE PLATFORM" to be on. I don't see why they wouldn't accept XNA made games but if we do use that we must make sure they do accept them.
Depending on what the next game is i'm going to make a suggestion, that I'll wait till psync meet to do as I'll no doubt have to explain for about 5 hours why I'd say such an outrageous thing

The beauty with doing something in C though I think anyway would be it could be ported to most things (though I may be talking tripe there) if we made the robot detective, iPads and iPhones would be a very nice place to take it for example, pretty sure that couldn't be done if it was made with XNA but how likely would it be we would get as far as to publish on iphones?
I'm not opposed to XNA if you think it looks decent and we can publish on steam, couldn't hurt to look into it anyway
