So, basically, it's an extended rehash of her Shadowbolts scene, only this time with the actual Wonderbolts offering her a place on their team. But then it turns out that the Wonderbolts are HUGE JERKS who ditched Soarin and had him fake an injury just so they could trick Rainbow Dash into thinking they need her, and Rainbow Dash decides she'd rather be seen in Rarity's ludicrously awful flower-patterned, unaerodynamic uniforms than participate in that kind of dirty trick.
Wow, they really made the Wonderbolts into a bunch of jerks. Lightning Dust would fit right in.
Also, she doesn't actually fly that fast -- she doesn't actually fly any faster than Fluttershy and Bulk Biceps, if you go by the stopwatch. I think if they wanted tension they should have given her less than 1/3rd of the time remaining to just barely get to the finish line with. That really bothered me.
Although not as much as Rarity's horrific uniforms.
Or Twilight Sparkle's wig. OH MY GOD.
Good things: Pinkie Pie's insane cheering, Flutter-bulk shipping, Applepult, and the crazy Wonderbolt pit stops when Rainbow was flying with their team.
So, yeah -- it's a good episode, even if it's a bit of a rehash. 3/3.
I also wrote a related story for a prompt... well, not really that related. But it was for a prompt theoretically related to the episode. Flying Hard