Lex Friedman tried out oodles of RSS services and apps so that you wouldn’t have to. He’s using Feedbin as the backend, syncing to Reeder on the iPhone, Mr. Reader on the iPad, and then using the browser on the Mac (this was obviously written before today’s ReadKit update).
Me? I’m using Feed Wrangler as the backend, syncing to Mr. Reader on the iPad and ReadKit on the Mac (while waiting for Reeder’s update that will support Feed Wrangler).