Quirky is an overused word, but it fits here

LIKE: A FIXED BASE
Running a campaign is much easier when the PCs are in the same place from one session to the next. Even if they travel, it's nice to have a "home" that they return to. It can be a house, a city, a geographic region - I like having a fixed base that serves as the starting/ending point of the action. It provides an anchor for the action, a recurring set of backgrounds/experiences, which help with the suspension of disbelief for both players and GM.

A fixed base is also a good place to plant subplots. If the PCs are going to see the fixer Black-Eyed Molli every couple of sessions, well, now we can weave her in and out of our larger action. When it turns out that her bodyguard Gus is the son of the tailor just down the street from the PCs' office, and that the tailor is the only eyewitness to a gangland crime, we can quickly sketch out a sequence of events that provide the PCs with a bigger emotional or material payoff. You save the tailor's life, and now Molli owes you a favor (or you don't and she makes your life harder). I'm a big fan of consequences in an RPG, and it's easier to see the consequences if you're connected to one place.

I'm also a world-builder. I like taking a location and fleshing it out. It's really satisfying to make a detailed and quirky place, and then reveal those quirks over time.

DISLIKE: SOLVING PUZZLES/MYSTERIES
This is purely personal, rather than some broad philosophical point. I don't like solving puzzles. Don't ask my character to do it. Don't make the adventure contingent on my doing it. If there's some cunning tapestry with clues hidden in its description, fine, let me make some kind of skill check to figure the damn thing out so that I can get on with doing the fun stuff. When I'm roleplaying, I want things to happen. Sitting around trying to outguess the GM is the opposite of happen. I think it's boring. This is one of my least favorite things about old-school roleplaying. I don't want to figure out the cunning riddle-box, and I don't want to hear all about the trap's mechanisms. Let me just roll some dice and get past the damn thing so I can get back to doing things.

The same goes for mysteries, Not in the sense of "something is happening and you have to figure out what" mysteries, but the "some clues are scattered around so go assemble and solve them" mysteries. When I read a detective story, I'm reading for the story part and not the detective part. I'm not trying to beat Hercule Poirot to the solution. I'm much more interested in watching the action unfold. If a GM has a brilliant mystery that they want me to experience, great - tell me about your idea over lunch. When I'm roleplaying, I want the focus to be on the actions of the PCs, not on the ideas of the GM.

EDIT: I would be remiss if I didn't point to this excellent piece by Jason Alexander. His "Three Clue Rule" alleviates a lot of my problems with puzzles.