Whoa, I missed something VERY big about iTunes 6. According to FutureProof from the Hymn project, if you use iTunes 6 to purchase even one new song from the iTunes Music store, you must use iTunes 6 for all future purchases.
This means that JHymn won't work if you update to iTunes 6. In order to break the copy protection, it has to pose as a copy of iTunes and retrieve encryption keys. But after you use iTunes 6, the iTunes music store will no longer issue keys to anything but iTunes 6. So until someone (probably Jon Lech Johansen) creates a version of JHymn that can impersonate iTunes 6, removing Apple DRM is not an option.