I am also interested in a news reader that can sync all my feeds across my iMac, iPhone and iPad. It would be great to make feed changes on any one device and have them all sync. Hopefully someone will add this feature to one of the existing apps if there is not one that already does this today.
I'm pretty sure the only way to come close to what you're looking for is to use Google reader and apps that sync with it.
Right now i'm using Google Reader in the Google Mobile app on my iPad and it is just "ok". Waiting for MobileRSS that I use on my iPhone to go native on iPad. I like it's features. Byline would be the next runner up when it goes iPad friendly.
Steve