This is a very cool example of how Ruby On Rails can make extremely minimize idea to working software time, and then iterate over improvements and enhancements in direct response to actual users (as opposed to the developer's own thoughts or artificial focus groups).

Well articulated. It is so true. I've put it up in no time, and now I have all the great input coming pouring in from people!
how about some self promotion? I've also put up bibli.ca about 3 weeks ago – this was my first RoR project – the one I learned RoR with.
It's directed at a much less active bunch of users, but none the less, I have a list of features I wanted to throw at it, and glad I did not, as the users, imagine that, have totally different things that interest them ;)