I really love Once Upon A Time. Everything about it works, even the occasional corniness and dodgey special effects add to the charm.
I've seen up to the fourth season. The channel that broadcasts it in Australia gave up on it after the third series, so after much angsting I had to catch the Frozen arc with a mixture of Netflix and illegal cunning.
The show reminds me a fair bit of Dragonball Z. Each arc is defined by the big bad currently opposed by the protagonists, and many of the more interesting protagonists were originally villains themselves, like Regina, Hook or Rumpelstiltskin. To my mind, Regina equals Vegeta, Rumpelstiltskin Piccolo, and Grumpy is Oolong.
What I really love about Once Upon A Time is how often insane things happen without seeming implausible within the context of the show. Like when Little John was attacked by a flying monkey, and became one himself. Or when Rumpelstiltskin needed ink in Neverland, so he summoned a squid, because obviously he can do that. Or when Baelfire summoned a dove when he needed to send a message. Sheer nuts.
All this said, I'm hoping that the show ends soon. When Emma became the Dark One I got the feeling that the show's story was around three-quarters over. These characters deserve an apocalyptic punch-up in which all remaining questions are answered, not to lose their appeal as the show is renewed beyond its relevance.