That's interesting, I think Rails has been overrated in the past but this is exactly the kind of project I think Rails is great for - where you've got a very clear simple aim, and you want to quickly develop an app people can play around with.
I am still new to web dev to comment on this. But IMO rails has managed well to take care of the heavy duty web apps as well. But yes as far as prototypes go and getting something built up quickly, rails is a definitely a good option.