-I'll admit that I had a bad attitude about this one going in. Let's face facts, the decision to bring back Trixie was obviously a response to her popularity within the adult male/EqD portion of the fandom. Which isn't an awful thing in itself--playing Where's Waldo with Derpy is something I enjoy, and that's nothing but fanservice--but considering how little of the fanon surrounding Trixie appeals to me, that influence understandably worried me. Besides, having established in her previous episode that Trixie is both a) irredeemably arrogant, and b) not really all that powerful, magic-wise (something too many fanfic writers seem to forget--one of the many reasons much of her fanon annoys me), I was braced for a truly awful episode from the moment I read the TVGuide summary.
Thankfully, I actually liked Magic Duel. It's not going to make my "favorite episodes" list, but it was mostly funny, dodged all my biggest peeves, and was all-around pretty solid IMO.
-That said, let's start with what I didn't like: medium-breaking humor. While I had no problem with Trixie magicking Pinkie's mouth off, the cursor/trash can joke killed it for me. I know that they have electricity and even computers in Equestria whenever it's convenient for a joke, but putting such an obviously modern intrusion into a show which generally eschews such annoys me.
-The super-artifact being randomly available in some out-of-the-way store probably wouldn't have bothered me too much by itself, but every episode this season except the CMC one has started with some major, ill-explained introduction into canon (the Crystal Kingdom, the duplication pool, and now the alicorn amulet). Is this just something that I'm going to have to get used to from now on? I hope that "previously unmentioned super-magic thingamabob of the week" doesn't become a recurring theme.
-One more really big one: Trixie and Twilight speaking unironically about how high their levels are. I hate, hate, hate it when a work of fiction starts treating itself like a game. I shudder every time I read a story in which wizards learn how to cast magic missile (or use vancian magic generally, Jack Vance excluded of course), and hearing lines about how so-and-so is the highest-level unicorn in Ponyville had me cradling my head in my hands.
-Lots of little things which I liked in this episode. For starters, beavers! I love beavers! Also on the list: uniquely designed ponies/horses from distant lands. Very neat appearance.
-Something I was very grateful for is that the fan shout-outs and continuity nods were mostly unobtrusive. Lyra (sipping a shake, no less) and Bon-Bon hanging out together in the background is a polite nod which doesn't detract from the show, in that anyone who doesn't know about the fandom won't be left shaking their heads and wondering "what was that all about?" for example. And the call-back to Pinkie's parents was a nice touch because it made sense in context--thank goodness for references that are both logically appropriate and not jarringly distracting.
-Lots of good humor in this episode, from Trixie's wheel-less (and ever-growing) carriage to Fluttershy's entire first segment. Perhaps the bit that made me laugh the most, though, was the realization that gender-swapped AJ was actually Big Mac (thank goodness for that, by the way--I don't think I particularly want gender-bending spells made canon). I can just picture the scene as he and the other painted ponies huddled behind the statue, awaiting their turn:
Okay Mac, you can do this. It's just a couple of seconds, but you've got to be so convincing that Trixie will never guess you're not AJ. What would AJ say? Come on Mac, you've got to get into her mind! Oh, looks like it's my turn--here goes nothing...-I have mixed feelings about the ending. While I'm glad the writers left open the interpretation that Trixie was just playing nice so that she wouldn't be lynched (her grandiosity isn't tossed out the window, huzzah), I wish we wouldn't have had the whole asking forgiveness scene at all. Let her run off again! There's plenty of lessons to be learned by Twilight and co.--no need to foist one on a character previously defined by her self-centeredness.
Tripping as she ran off was a nice touch, though. Like I said, a lot of little bits of comedy that worked for me, and that left me pleasantly surprised with the episode as a whole.