Dr. David Mobley, at Pediatric Associates of Plano. Both he and another there, Dr. Jeanette Smith, both came highly recommended to us from several sources, including parents and the doctor that delivered our son. Their office is at Plano Presbyterian, at the Tollway & Parker. The office staff is very friendly and helpful; they're happy to answer the dumbest questions from first-time parents (we have a 7 month old). For instance, my wife recently took our son to see Dr. Mobley because she thought he had an ear infection. Come to find out, he had simply just discovered he had ears, so he was touching them all the time.
The nurses call back to answer questions quickly, and my wife hasn't ever waited more than 5 minutes in the waiting room.