Mark Waid mentioned on Fanboy Radio (paraphrasing from faulty memory) that part of the Plutonian's hang-up/flaw/etc. was not being emotionally stable enough to handle being a superhero.
I've wondered why Superman's super-hearing *doesn't* drive him nuts, even if he doesn't have it "on" all the time. Waid's comments got me wondering if there's something about Superman's Kryptonian yellow-sun powered brain that keeps him on an "even keel."