I certainly think it is a worthy cause. I am not, nor have I ever, used a Mac or OSX so I can't comment on how easy or difficult it is to get up and running with Ruby or Rails for that particular environment. There has been quite a bit of talk about this and it seems there are several people with projects trying to make Ruby development easier on OSX.
I personally use Linux (specifically Fedora) for development and while there were a few challenges in getting everything set up, I think it was relatively easy.
Time will tell how these projects pan out and if they truly make entry into the Rails world any easier.