Rotten Tomatoes is adding TV show ratings. I heard about it driving in to work on the Kevin & Bean show (on KROQ in Los Angeles). Their TV Zone is currently in beta and not all shows have ratings, but the example their reviewer used was Agents of SHIELD, which scored really high but then dropped slightly to an 83% by this morning.

Seth MacFarlane's Dads has the honor of being their only show currently rated at 0% (ouch).

http://www.rottentomatoes.com/hub/tv-zone/