"Parser" said the really wrong thing to me. Notification and normalization seems to be what's going on but you still need to parse the Atom feeds. "Parser" says to me something like http://www.feedparser.org/ . (Kind of by definition, a "web service" to "parse" another web service is absurd.)
I'm not saying this to be critical, just to let you know what I saw when I tried to read your site.
Very nice service. I would've used it for my project had it been available when I started, but I had to build most of the features you listed in house (we pull about 80K feeds). One feature that might be interesting to add is returning the results in json format since that's easier to parse now that most modern languages have that built it. And, by the way, are you aware that Google offers similar APIs? They restrict using it to personal and non-profit, so I couldn't use it.
But AFAIK, this API doesn't offer to actually do the polling for you. In the end, you would still need to spend a lot on BW to guarantee you get the updates in a timely manner. Also, (and that goes with the previous point) they cache the results from feeds... which is really not what we want to ensure fast detection of updates.
I'm not saying this to be critical, just to let you know what I saw when I tried to read your site.