I just went and built something with it - http://alltimetop5.com
I'm shocking at busy work for no good reason so I had to wait until a good enough idea came along to motivate me. The first version I just threw out, there were too many artefacts left from me stumbling wildly around.
I think that might be the point where you can call yourself proficient at ror, when you finally get how ugly the first code you wrote was :)