I was not interested at first, but I ended up enjoying it. The best part are Uncle Grandpa's interactions with the Gems. Pearl channels Squidward, Amethyst gets a dizzying ecstasy from Uncle Grandpa's reality bending and Garnet calmly admits that she's ready for the episode to end.
The scenes of Steven in Uncle Grandpa's Winnebago drag the pacing down but the rest of it is really worth a watch.