I've been using C# to program an XBOX Live Indie game with a friend of mine so that we can fatten up our portfolios to get hired at a game development studio. I wouldn't chose C# by choice over C++ or even Python given the opportunity, but it is a nice language to use.
I hear the studios are not considering XNA projects as portfolio work because it does not show your ability to develop an advanced C++ game that utilizes DX or OpenGL.