Just for those looking for .Net wrappers the correct (current) 2 are:

http://sourceforge.net/projects/irrlichtlime/ - the development of irrlich.net stopped in favor of this project, and it has made an updated release this year.

http://www.ogre3d.org/tikiwiki/tiki-index.php?page=MOGRE - the development of OgreDotNet stopped in favor of this project, but even MOGRE is only at OGRE 1.7 instead of 1.9

I haven't used them so I can't speak to their quality or completeness, I just know that all the other .Net wrapper projects seem to be dead, so these are the best options as far as I can tell. And yes, the OP wasn't asking for wrappers, I just wanted to provide the best links in case someone following this thread goes that route.

To the OP, I haven't used Unity, but I came to C# after 7 years of C++ and it was not a terribly hard transition. The 2 biggest issues I've had being in C# instead of C++ are: The lack of the C++ Standard Template Library, and the increased difficulty of accesing Native C++ libraries - which can be an issue in games development. For NON-game development tasks, I have found C# more enjoyable than C++ in almost every case, but occasionally while messing around with hobby game stuff, I still find the C/C++ to .Net bridge to be a little annoiying to have to deal with (like that fact that you have to hope someone maintains a decent .NET wrapper and doesn't deviate to much).