Commander Video. His warp zone had soooo much potential, I was expecting visuals similar to the BIT.TRIP series of games (And that would have been, awesome), but it didn't really have anything at all. Just a random barrage of colors that would probably give someone a seizure. And I've never really used him all that much, except to get the warp zone in World 4 Dark, but even that's barely anything notable.
As for Jill, I'm happy with her, mostly becuase her warp zone actually looks somewhat like the game she's in (it's sorta Gothic, maybe it doesn't resemble the game, but I think it does). Not to mention she helped me get a couple of bandages in Rapture, and Flywrench's warp zone didn't resemble the game, but he is a rather cool character. Commander Video is cool, but other than that, he's got absolutely nothing I mentioned.
Ogmo had the best warp zone IMO.
It actually looked something like the original Jumper, it actually made you use his ability, and it wasn't that hard (For Salt Factory standards, anyway). I can't say anything about the Kid yet, because I haven't beaten his warp zone yet. But, based on what I have cleared, it's not really that bad, just hard. Very hard.