Not a Google Reader user (i used iGoogle until they discontinued it on smartphones...), but it's really a great site, congrats. I'll probably go get a look at the source since i'm an angular and app engine user (and not really serious with go...yet).

One small question : is there a reason why you need to go to the top right menu to add a new stream, instead of just a "+" at the bottom of the left pane list of feed ? Is that what google reader required ?