I've read about it in Ian Joyner's C++ critique, but I never tried it. Eiffel is supposed to be a "pure" OOP language if I remember correctly, and personally this makes me less willing to learn it.
I am reading "Touch of class" by Bertrand Weyer, He tries to explain OO using as an example of a programming language Eiffel. I did not download their EiffelStudio due to some warning of Windows during loading. So I read it simply as bellers lettres without trying any example of code shown in the book.
It seems that I am the only who read this book.:)
So after reading it I can append my resume that now I know neither C++ and nor Eiffel however I can talk about them.:)
We looked at it back in the early 90s; all that C++ bashing and emphasis on pre/post conditions ...
Abrasive characters are not endearing, and Bertrand Meyer was certainly that. And after the Smalltalk vs C++ wars, I was in no mood for round 2 with Eiffel.
It kind of reminds me of that Scala guy who joined the forum some time ago to tell us of all the things that C++ was allegedly bad at and how Scala could do it in one line.
In summary, good ideas; difficult environment; no, not used it.