I remember that addFinalizer never did work quite the way people expected it to. A current instantiation of this problem: adding a finalizer to a ThreadId. Could somebody please give me a short explanation why the following never prints "Finalize"? [ghc is 5.04-cvs]

Your finalizer runs right at the end of the program, after the stdout Handle has been closed, so it can't print anything :-) Cheers, Simon