Raphael Simon and Emmanuel Stapf, the Eiffel developers, have an article on MSDN. Its an updated version of an earlier article and describes the current state of Eiffel for .NET - which they claim supports the full language.
The article describes support for MI using interfaces. It sounds a bit of a hack and it will be interesting to see how it works in practice.
I've downloaded and installed Eiffel Envision, the Eiffel plug-in for Visual Studio. I'm planning to write a review of Envision but the first thing I attempted was to implement an XML-RPC client. I had to seek help on how to specify custom attributes but otherwise it was fairly straightforward.
