You're right that on most things, Ron Paul is firmly grounded in conservative principle.
The one issue where I would say he is not, is in his advocacy of surrendering a war to barbarians for no good reason (i.e., because we're "tired of" it). There is nothing particularly conservative about that stance, except in the most uncharitable definition of what it means to be "conservative" (i.e. cowardly, insular, lazy, sedentary...).
And the thing is, it's that stance alone which has given him this mini-swell of popularity. It's not like the antiwar kiddies love Ron Paul for his anti-tax platform. Hell, it's not like they even know anything about his anti-tax platform, or anything else for that matter, besides the fact that he's "against the war".
No offense but there's nothing particularly conservative about carrying out Wilsonian nation building. Nothing to do with cowardly, lazy, or sedentary. But rather you declare war, you go to war, and you win the war only when necessary and not to 'stabilize' a region or remove a dictator that may or may not be supportive of actions against another nation not ours.