I'll cut to the chase: Pinlock works!  Over the past 2 winters, I've chronicled my search for a solution to motorcycle helmet visor fogging that is effective, simple, and long-lasting, while contributing as little vision distortion as possible.  My search is over; Pinlock scores on all criteria!  The "smear-on" anti-fogs I tried were effective to varying degrees, but many were fussy to use, most didn't last very long (particularly with rain or inner-shield condensation in the mix), and all caused unacceptable visual distortion.  The "barrier" methods I tried (Respro Foggy mask and Arai's breath mask) were effective and caused zero distortion, but proved very fussy to use with eyeglasses and each tried to rip the flesh off my nose and forehead when removing my helmet.  Many folks seem very happy with the Respro, so it may just be my particular head shape/helmet fit, neither of which I plan to change.  

Though Pinlock is very popular in Europe, we Yanks seem to be Pinlock-deprived for some reason (perhaps liability-related). After searching in vain at local dealers and many Internet sellers, all of whom were alleged US Pinlock retailers (Pinlock won't sell direct), and European retailers who refused to sell to the USA, I managed to score one for my Arai Profile from Rusty at Motorcyclecloseouts.  The Pinlock  system comprises two parts: a Pinlock-prepped visor (meaning it has 2 pins installed) and the Pinlock insert.  Pinlock allegedly sells the pins in a DIY kit, but you likely won't find one for sale in the States.  Many helmets come standard with Pinlock-prepped shields in Europe. The insert is made of a moisture-absorbing plastic and has a silicone beaded-seal on its perimeter.  In addition to clear, the insert comes in the usual array of visor colors. Installation is simple:  butt the notch on one side of the insert against one of the visor pins, flex the visor carefully, and butt the other side against the other pin, and relax the visor (see detail below left).  The silicone bead forms an instant seal against the visor.  The insert can be removed and replaced at will for cleaning for changing weather or light conditions.  I installed a clear insert and probably will remove it only for cleaning as I've never found much use for colored visors.

I initially experienced some interference between the top center of the Pinlock's bead and my Profile's eyeport gasket.  After some consult with Arai, I shipped the helmet and Pinlock to it's awesome service center, where a tech made some magic adjustments to the helmet that worked wonders.  I had the lid back the next day and all worked well.  During the past couple of months, I've used the Pinlock in myriad conditions: fog, rain, a little sleet, one small hailstorm, and low temps ranging from the high 40s F down to the mid-teens.  During all that, the Pinlock insert has been 100% fog-free, even with the visor locked-down to the max, and even while stopped in traffic.   Is it perfect?  No. In the dark, the Pinlock causes a very slight degree of "back reflection" from headlights and streetlights, but no forward-vision distortion.  And while the Pinlock insert has been 100% fog-free, the periphery of the visor not covered by the insert fogs up, resulting in some loss of peripheral vision, though the range of loss is minimal and the trade-off is well worth the safety of fog-free vision in the larger degree.  The range of loss is larger in Arai helmets due to Arai's eyebrow vents (please get rid of these useless vents Mr. Arai).  This last observation is also being addressed by Pinlock, which is releasing a new version of the insert, the "Max Vision", which covers nearly the entire visor and sits in a recess in the visor instead of using mount pins.  I understand that the Arai version with be sans eyebrow vents.

I'm now riding fog-free in the nasty stuff for the first time ever.  No more fumbling to crack the visor open with heavy winter gloves while coming to a stop on my commutes, no more rain-intrusion from a less than locked-down visor, and better vision ups the odds against brain-dead cagers and kamikaze deer.  Every helmet sold should be Pinlock-equipped; all mine will be.