I'm going to agree with The Avalanches in adding a Trick Room set in here as the second main set; even though Trick Room is fairly niche, Pumpkaboo is, from what I understand, one of its premier setters.
Overview:
Mention being able to simultaneously wall and spinblock Drilbur, the most common Rapid Spinner. This is arguably the biggest reason to use Pumpkaboo, so put it near the top; other Ghost-types are hit hard by Earthquake, but Pumpkaboo's decent defenses and semi-unique typing allow otherwise.
As fitzy mentioned, the two points on how Pumpkaboo compares to other formes aren't really true; in addition, they're not very important in the first place because the other Pumpkaboo formes aren't hugely notable, so those two points could probably be removed.
Standard Super:
As The Avalanches mentioned, is there any reason you're running Seed Bomb over Bullet Seed? Bullet Seed crushes Sturdyjuice Tirtouga and deals more damage on average. I think Seed Bomb should be entirely replaced with Bullet Seed; don't forget to reflect this change in the Moves section.
I don't think the "Revenge-killer" and "Wall" points should really be left in under usage tips, because Pumpkaboo is neither a reliable revenge-killer or wall for the vast majority of the metagame, so this is misleading; I feel as if the tips themselves are really common sense.
Checks and Counters:
I don't think Litleo needs its own mention because it's not all that relevant.
I'm going to withhold QC until I have a look at your Trick Room set, but otherwise, this is well done.