The last time I felt like that about a show was during Heroes Season 1 ... ya know, before they dropped the ball so hard it left a dent in the Earth's surface.
On the other hand, Once Upon a Time just gets more and more intricate and yet everything works together so well. The show is very well casted (Rumple and Regina especially), the flashbacks to the magic kingdom are genuinely interesting and far better than most of the REAL fairy tales, and overall the show just has me waiting for each and every Sunday without having let me down yet. Oh, and whoever the hell writes this show ... they need to hold onto them and never let go ... I have literally lost count of the number of shows that go to shit due to writing or producing changes.