I won't ever vote against someone.
If I don't like you, you don't get my vote. Nothing more to it.
“Tyranny is defined as that which is legal for the government but illegal for the citizenry.”
― Thomas Jefferson
It's kind of like what Douglas Adams said about Zaphod Beeblebrox. Ideal Presidential fodder is the guy with the big ego and not much else.
So you end up with a combination. Sometimes you vote against the incumbent because he hasn't done his job very well, even if you're not completely convinced that the new guy is all that much better. Sometimes people surprise you. So I'm leaning toward Romney. I'm not convinced that he's all that great, but we know Obama isn't. I hope that Mitt is one of those guys who will do a surprisingly good job.
(God, I am far too cynical...)