I can just hear Glomgold now: "What happened? Did you earn your key??"
* SPOILERS *
Sorry to say, without the "key" business, I would have ranked "Falls" as a below-average effort. The set-up is a "losers vs. bullies" scenario straight out of Race for Your Life, Charlie Brown (1977), with Rainbow attempting to goad a motley crew of pegasi into qualifying for the relay races at the upcoming Equestria Games, directly in the teeth of a challenge from the unpleasantly arrogant Wonderbolts. The script papers over the obvious logical issue inherent in Rainbow not being able to pick a better team by having a character state that competitors can only be in one event at the Games. Even if you buy that excuse, it's still hard to believe that Rainbow couldn't have scared up better representatives of Ponyville than the ever-reticent Fluttershy (hasn't she learned SOME self-confidence by now?) and the absurdly bottom-heavy Bulk Biceps (who, to add insult to injury, was shown to be a competent flyer in several previous eps but is "retconned" into a muscle-bound clutz for the occasion). With Pinkie Pie at her most grindingly irritating as a way-over-the-top cheerleader and our "heroes" struggling to manage even the barest smidgen of competence, the opening minutes of the ep are painfully embarrassing.
Rainbow's "test" comes when one of the members of the Wonderbolts' team hurts his wing and Spitfire convinces Rainbow to help the 'Bolts train in his absence, even as Rainbow is trying to get her gang to straighten up and fly right. The inevitable offer to join the 'Bolts for good comes soon thereafter, and Rainbow is legitimately torn, so much so that she feigns catastrophic injury... badly... so that she won't have to make a choice. Rainbow's "performance," which makes one of Rarity's "drama queen" fits look subtle, normally would not fool anyone with an IQ higher than single digits, but everyone (save Twilight Sparkle, who's been trying to get Rainbow to do the right thing throughout) is conveniently dumb for the duration.
After Rainbow learns that the Wonderbolts' injured partner could have flown in the trials after all, but had instead been ditched for Rainbow because she's the better flyer, she takes the side of Ponyville and helps her team to (just barely) qualify for the Games. This is what prompts a repentant Spitfire to make Rainbow a gift of the pin. Interestingly, both "pin events" thus far have included a "Mane 6" member both surviving a test of her nature AND inspiring another individual to behave in a better manner. In a sense, both Rarity and Rainbow have become "ambassadors" of their Elements. And, even from the little advance notice that has leaked out to date, it's become pretty clear who will be next character to assume an "ambassadorship"...