The ending of S3 as a whole was actually pretty enjoyable, and I like the ideas they had for the episode.
It pissed me off because of how hard they rushed the damn thing. I would've liked it if they split it into two parts, making the first episode the whole cutie mark swap bullstuff, then Celestia coming back for a "special surprise" and making Twilight all worried/excited as a cliffhanger, and the episode after that would start out with the corination, then Twilight actually doing princessy bullstuff and seeing how stuffty it is, missing her friends and resigning as princess.
That would be pretty neat.