I unscientifically believe that DEET is freaking poison. I've had no option but to use it daily for about six months when I was 18 and pretty much ruined my skin. Plus I felt sick for months after that.
Picaridin from Sawyer felt pretty harmless in comparison on exposed skin, and it worked for me so far. Never tried Permethrin, but it sounds a bit like overkill for ticks. Light colored long sleeves and pants in combination with dorky fashion sense (shirt tucked in pants and pants tucked in socks) work pretty good in ticks infested areas - added bonus is that chicks dig the look too. I believe that bushwhacking through shrubs and trees is the easiest way to acquire ticks on your head, back or other areas of body where you can't notice them quickly before they migrate under your clothing. Not sitting on grass and piles of leaves also helps. But I'm talking about East Coast precaution measures, I could be mistaken but chances of collecting ticks in CO are smaller by the factor of ten or so.