I liked how it came out! I was one of those people who didn't care which one got picked for the show. Although I was expecting "The character is based on the author" plotline, I have to admit I was blown away on the Author literally BE the character, even if they stuck with the "author" plot I was expecting I still would've been fine with that.
Even if there are others who didn't like the execution, there are two redeeming things I find about how it ended up.
One: It had some rather funny moments, I can't help but laugh at how Pinkie Pie said "Or maybe A. K. Yearling is just a Terrible, Horrible, Unbelieveable SLOB!!!" To me that screamed "That's Pinkie Pie!"
And Two: It could've been far worse! When I heard the premise was "Rainbow Dash learns that the next Daring Do book is going to be delayed, and insists to her friends that they need to go help the author A.K. Yearling to finish the book faster." I thought it was highly likely the writers somehow made RD a little too selfish... Which she kinda was, but I was glad Twilight wanted to put some sense into her and the focus quickly changed from "Forcing an Author to write ala "Misery" to "anxious fangirl" in less than half the episode, they dodged a bullet on that one!