Ron Paul is (in my opinion) pretty good on social policy, he's basically a Libertarian, and his position on everything is pretty much "the Federal gov't should stay out of it".
He's a fiscal conservative, in the sense that he wants to reduce the size of gov't. . .also a big plus in my opinion.
Unfortunately, as a candidate, he's severely flawed in two ways:
a. He's a foreign policy isolationist. He wants the USA to retreat into its shell and not worry about what happens in Russia, Iran, China, Israel, Afghanistan, etc. IMO, even though on paper it looks good, the reality is that an isolationist policy isn't good for anyone (well, except fascist dictatorships and human rights abusers, like Iran, etc), let alone the USA.
b. Paul has a long history of association with all sorts of political cranks, like Birchers, 9-11 conspiracy theorists, Neo-nazis, and the like. He used to publish a newsletter catering to these cranks that included a bunch of questionable anti-gay, anti-Israel, and borderline racist stuff with his byline on it. Now, that doesn't mean he believes everything they believe, or even most of it, not does it even mean he believes what he put into print. Objectively, none of the things in his newsletter are any worse than the racist/Jew-baiting garbage that President Obama's "spirtual mentor" Jeremiah Wright used to preach every single week.
But regardless, to me these last two things are disqualifying. Feeding into all the worst stereotypes of Republicans, I simply can't support this guy for Republican nominee.
I fully expect him to dry up and blow away after Iowa. Last election cycle he capture more than about 5% of the Republican primary vote. This time, due to a variety of factors he'll probably do better, but I can't see him winning New Hampshire let alone SC, and after that its going to be all uphill for him.