This episode was alright.
I disliked the fact that the rest of the Mane 6 were so inconsiderate to Twilight's feelings in this episode. They somewhat made up for it in the end, but it was not explicitly addressed well.
Nonetheless, the message was very good. Jealousy is a real thing in friendships, and it was good that they addressed it. I think the fact that this episode rubs many of us off in the wrong way means that the writers did a good job of making us empathize with Twilight and her struggle.
Also, this episode further solidified the fact that though Twilight is the Princess of Friendship, she is definitely not perfect. When bronies first heard of Twilight becoming a princess, weren't at least a handful of them afraid that she'd become some sort of Mary Sue? Well, this episode definitely emphasizes the fact that this is not the case.
A good friend of my on another forum mentioned how Discord had these same feelings of jealousy in "Make New Friends but Keep Discord". We've seen in episodes like "Three's A Crowd" that Discord likes to give Twilight twisted tests, so this is no different from that. The difference that make this episode seem "worse" is that Twilight had a worse struggle.
Overall, I don't think that this episode was bad. It's not my favorite S5 episode so far, but that doesn't mean it's not good.