One thing that hasn't come up is that the increased resistance to air flow might hinder performance, let alone whether there is a benefit to warming and HUMIDIFYING the air (which, as far as I can tell, is the primary reason for wearing the mask - I say this because it's done in some other sports for warm-up periods. Some pro teams do it on long flights, partly to filter air of allergens/germs, but also to humidify the air).
Salazar alludes to this resistance issue when he says that their mask forced you to breathe harder. That's because the increased resistance makes the work of breathing more difficult. If you've ever done a VO2max test, you'll know that the resistance through the tubes and mask is pretty unpleasant.
There are some studies where helium has been added to the mixture of the inspired air to try to reduce the work of breathing. We did a couple of those, but they were inconclusive, probably because the work of breathing is not limiting in a healthy population doing maximal exercise. In people with COPD (obstructive pulmonary disease), there is evidence that helium breathing can improve performance: http://www.ncbi.nlm.nih.gov/pubmed/16439720 (there are some other studies on this too).
However, in healthy individuals, I've not seen a study showing this for maximal exercise (or anything like it takes to run a 60min half).
Rather, I suspect the opposite. That wearing a mask is at best doing nothing, but at worst increasing breathing resistance. Does that offset a POTENTIAL advantage from warming the air? Who knows? There is probably an advantage to humidifying the air, but it's largely perceptual - it's not as though the body fails to warm air effectively at 35 F. But perceptually, it might make a difference, so Rupp was "managing his perceptions" (to use a euphemism).
It does look funny though. I'm all for natural, no gimmick running myself. Breathe-right strips are hard enough to have to discredit to people who want to know if they work...