I love TH (though not as much as metalua and metaocaml), but I've never had the occasion to use it. I've used a library that uses TH to parse out my prop_foo into a main method that will run all the quickcheck tests, but that's about it.

Is there any particularly well-done TH being used somewhere in the real world? (You don't have to show me the code, just what problem you had that TH solved.)