Just thought I'd report in on the pain factor: I found it wasn't so much painful as shocking, like getting a series of small electric shocks, worse along the lip and the jawbones where I seem to have the most nerve endings. There's something about not being able to see what's going on that heightens the shock factor, and the jet of cold air blowing unexpectedly up my nose freaked me out when it happened 🙂 - but all in all, not a big deal.