Now that Clojure is at 1.0 and a book is about to come out I definitely feel comfortable using Clojure in a production application. It's a thin layer on top of Java and I can easily fall back to Java if I run into problems with Clojure. The IRC channel and mailing list are also available (and very helpful) for asking question.

I'm working on a commercial website using Clojure and Compojure. Should be out of stealth mode in a few weeks.

See http://www.infoq.com/news/2009/01/clojure_production for an example of Clojure being deployed in a hospital.

(edit updated with description of link).

Sure. I'm curently working ot cross platform desktop application, but that's all I can say.