SuperFeedr is awesome and Julien is great to work with as a user of the service. I wish they had this feature when I was working on my multi-medium client (now defunct) a year and a half ago.

The only downside—and why I stopped using it—is that the pricing model is per-item, so if you have frequently updating feeds it can get very expensive. Although I never tried to use it, the pricing page does say they they'll meet whatever it costs you to run your own feed system since their cost should be lower than yours.