Second Life and Mono
Today the scripts running on Second Life are a bit slow, so they are looking at Mono and the CLI as a way of providing more speed to their users and hopefully allow developers to write in other languages other than their Linden Labs Scripting Language.
They have a compiler that translates their scripting language into CIL bytecodes, and the preliminary results give a performance increase between 50 and 150 faster execution with Mono.
Yes, people actually do use Mono in “the real world”.