Overall good idea, but I'd say: obviously I wouldn't use this for my regular feeds, only for some specific ones for which I want live notifications. So maybe some basic filtering options would be good (by keyword, by author...). (Or maybe it's implied people would use existing services for filtering?)
Filtering is one of the possible features indeed. I've added a suggestion here: http://rssim.uservoice.com/forums/40421-general/suggestions/... if you need it, vote for it!