Title says it all, has anybody used MonoGame before?
I'm especially interested in how the performance is, I know there's some commercial, shipped titles that were developed on top of it so I guess it can't be too bad performance wise but maybe somebody has some further experience with it.
I'd also be interested in usability and in how low level you can get with it as I'm coming from a C++/OpenGL background but am evaluation options for a team project with a team which is mostly inexperienced with C++ and I too would appreciate some kind of groundwork.

To round up this question, if anybody has experience with C# for game development in general (I know there's a least one person here), especially in terms of performance, I'd appreciate an opinion.

C# is pretty neat for game development imho.
It allows you to create complex structures without loosing track of the project structure.

MonoGame/XNA is basically a DirectX 9 wrapper (altough MonoGame uses GL under Linux).
I don't have a good experience with level design as MonoGame has no built in level editor (it doesn't even know the concept of a "level").
You must build everything yourself, even more than with Gamestudio. Yeah it takes some dirty work (loading textures, input, windows, ...) but it is not more than some kind of framework for writing engines and/or games.

You should take a look at some example projects to see how to work with it, i think this will explain best how MonoGame works.

Performance should not be a problem as mono and the .NET framework have a pretty good JIT compiler and you mostly don't do "heavy" stuff

Regards
Felix

PS.: If you ask for something specific, i may can answer the question.

"even more than with Gamestudio" - well my last project was build more or less from scratch with OpenGL and a simple platform layer library so that's not much of a problem.... It's much more the contrary, I'm interested in how much I CAN do myself, like writing my own renderer on top of the GL/DirectX abstraction layer. So far it looks really good because it doesn't seem to pose any limitations in that regard which is nice. Thanks for the reply Felix, if more specific questions pop up I'll be sure to come back at you.

Just one small note: Reach/Full under XNA will kill you. I don't know how it is with MonoGame, but some Restrictions in XNA are just PITA.

What kind of restrictions would that be?

Have something in mind with multiple render targets and floating point targets are not possible at the same time.

Sooooo multiple floating point render targets would be impossible? Or a deferred rendering pipeline with HDR support?

Let's say it with this words: I couldn't create a HDR renderer.

But that was with XNA, not MonoGame. Maybe it will work with MonoGame, dunno