Exactly! We've been doing the same thing – releasing only to GitHub because it's so easy and fun (and easier now that they e-mail you when the gem fails to build...)

The idea behind Joe is that if you're already releasing to GitHub, it's really easy to release to RubyForge as well with a single command. No need to wrap your whole project inside something like Hoe. You're already generating a gemspec for GitHub, why not using it for RubyForge?

Plus there's the addition of the ERb template to produce the gemspec (which is completely optional), but that's the best way I've found to maintain my gem specification, especially the files I want to ship.