It's a cool concept, but I can see everyone comparing it to RapGenius (several people in the thread already have). RapGenius has a bunch of features that seem t

It's a cool concept, but I can see everyone comparing it to RapGenius (several people in the thread already have). RapGenius has a bunch of features that seem to be missing here, you'll probably have to justify their absence. The biggest problem I see, however, is the slideout pane from the right when you click an annotation. RG does this without taking up the whole reading area; it seems a bit silly to reproduce the whole sentence being annotated and cover up the rest of text for one heavily padded tweet. Personally I would find a two-mode interface more useful: hover to see a small dialog with the top/newest tweets and a summary of the annotation activity, and click to get a larger overlay if there's too many tweets for the small view. Finally, I think using pg's essays might actually hurt you. I get that it's a gimmick, and the HN crowd might like it, but I think the man himself might be less flattered and more put off if it seems like you're trying to make up for technical shortcomings by flattering him.