This series succesfully shows the exact opposite of blockbuster movies: Create a great story with mediocre special effects and lesser known actors.

The writers behind this show do an amazing job creating one wonderfull Fairy tale adaptation after another. I did not like their previous work, but I think the writing is getting more mature (but they still make some errors that are frustrating.) But mostly they are not afraid to change major aspects of the fairy tales if necessary.
The creaters of this show also worked on 'Lost' and the 'TRON: Legacy' movie.

I really love how Rumpelstiltskin plays the evil maniac, especially during the first season. But there are more noteworthy roles in there, like the evil queen, her mother, Belle, Hook or Peter Pan. Emma Swan is pretty well played, but compared to the extreme characteristics of the fictional characters she is a bit bland.

The things I dislike most are probably some repeated main themes (family feuds/bad parent-child relations) and that they copy the characters of fairy tales a bit too literal from the Disney franchise from time to time.

Overall I think it is on of the best non-comedy shows of the past few years.
PS. I am glad Lady Gaga never replied on the invite to play the Blue Fairy.