I liked it. The primary message is a good one: "If something sounds too good to be true, it probably is." The secondary message about what happens when we limit ourselves due to our fears is also important.
This is more in line with the Flim Flam brothers than the previous encounter, where their machine actually did work. This time around, we see them selling snake oil (well, applejuice and beet leaves) as a "curative" tonic, which is an obvious fraud, the tonic being nothing more than a placebo.
As humans we can relate to this, because we have that same herd mentality, where if we see others being "cured," or benefiting from something, then we want it to, and we're more likely to believe it. That's why you see so many personal testimonials on websites shilling such snake oil, because those can be made up, and they'll still be believed by a percentage of the population who wants it to be true.
Applejack shows this by suspending her disbelief in order for Granny to be happy, and while her intentions were good, the road to Tartarus is paved with good intentions. From that point forward, things spiraled out of control. Which brings us to our third message of the episode: It is better to know the truth than to believe a lie, even if that lie is a comforting one.
Honestly, the analysis episodes will have a field day with this one, as there are a number of strong, positive messages in it that can be elaborated upon. Even myself here, as I don't normally post a response this long after watching an episode, at least not at first.
Still, this episode stirs something in me. I am a skeptic, and a critical thinker, and this episode rings true with me because of its layered approach to what harm there is in "magical" thinking, when someone believes a lie because they find comfort and validation in it, even as it may cause them great harm farther along the road.
So this one gets an "A" from me.
Also, Big Mac wears a rubber ducky floaty ring. Instant win.