I really liked this one. It's fun to see these two immortal, demigod princesses taking a road trip and kicking back like anyone else. It's really something to see Celestia cutting loose on the zipline, for example. I especially liked the shot of them chilling on the peach wagon. The song was very good.
Captain Celestia and Super Luna were fun to watch.
I did sympatize with Luna...she had a point about Celly always wanting to do her thing and disregarding what Luna wanted to do or if she just wanted to take a break and rest. But it's true that Celestia may have acted that way because she's used to having to consult others for things, as compared to being able to do what she wants. It's unfortunate that it led to thier argument, but they worked it out in the end.
Celestia's "I do know." remark was touching. Maybe she was reminded of what can happen if you don't pay enough attention to your sibling's opinions and needs.
I liked how the episode ended, maybe saying that even when Twilight and Co. are in charge, Celly and Luna will be there for them if they really need them.