Rating: 

Small quibbles - one of the example apps didn't work as it was supposed to, apparently because of a change in Rails. However, Kevin was very helpful in working with me to find the problem and suggest workarounds, so kudos to him.

I also wish there was more information on setting up larger data structures. Right now I get that it's possible, but it still seems intimidating and error prone.

However, those are only minor detractions from an otherwise excellent writeup!