Picaridin(sp?) is proving quite effective for me, and I hike off trail a lot in MS, sometimes in or near swampy areas.Mossy and tick heaven! Permethrin (sp?)has turned out to be wonderfully effective. Very often these days, I hike with a sun hat (with one of the cloth thingies that hangs down to cover neck and shoulders) and socks thoroughly sprayed with Permethrin, pants and tee shirt less thoroughly sprayed. (that is sprayed mainly around waistline, cuffs, neck opening etc) Then I carry Picaridin just in case, for remaining exposed skin. But most of the time, I have not had to bother applying the Picaridin.
But either way, I never even see a bug near me these days. In the past, no matter how much DEET or Picaridin I would put on my face/neck/ears, usually I would hear that irritating buzzing right near my ears soon after getting out of the vehicle to start the hike. I usually couldn't see the rascals, and I wouldn't get bit. But it was a little disconcerting, and I would often stop to add more repellent around my ears due to paranoia. These days, I suppose due to the Permethrin sprayed hat and clothing, I rarely- if ever- hear that dang buzzing. I love it!