Believe it or not (well you probably believe it...) I finally got around to doing this for Changeling. About time too.
Truly Cool:
Redcaps - There's very little not to like about redcaps. The only problem I see is the fact that they're hard to fit into parties, especially if the other members are whiny nancy-boys who can't stand a real Kithain in the group. Hey, those momma's boys have got no business complaining about Redcap eating habits, unless said habits are other members of the group. Redcaps are the toughest kith, excepting maybe some Trolls. They're very cool looking (okay, this depends highly on the picture you're looking at, but their description is cool). And of course they're from Scotland. That always helps.
Nockers - If I were to play Changeling, I think I'd be a Nocker. Sure, they're surly, foul-mouthed little suckers, but they're incredibly useful to have along. I think I could definitely while away the hours between games by coming up with zany new inventions to build. Even though they're almost as anti-social as Redcaps, they're usually more tolerated because they're not as dangerous to their fellows and because a fixit man is more useful than a bully in a lot of situations. And even though their physical description walks a fine line, in the end I think it works pretty well.
Sorta Cool:
Satyrs - Everybody loves a satyr. That's got to be a universally accepted fact in Changeling. Now say it with me: Satyr chicks. The problem with them is that they're not that great in a long-range, serious campaign. Eventually they either start to get on peoples' nerves or they lose part of their satyr-hood.
Trolls - Big, strong and honor-bound. What's not to love? Well, they might be a bit too straight-laced. There's very little you can do with them as far as idiosyncracies go. But they're pretty cool indeed.
Sluagh - They have no teeth, man. But dressing Victorian and speaking in whispers is a plus. They're also annoyingly anti-social, without any real reason to be, unlike the Nockers.
Not Cool:
Pooka - Annoying as all crap.
Sidhe - Nobody likes the sidhe. Sure, they're the knights in shining armor... but nobody likes the sidhe.
Boggan - Great, if you want to be a sidekick. And a sidekick's sidekick. And a sidekick's sidekick's...
Eshu - The problem with playing a traveler kith is that probably the campaign will take place at a certain spot, so living a life on the road will be out of the question and you'll have to think up a pretty far-fetched excuse for why your Eshu keeps going back to the same place game after game after game.