I've tied some sculpins with the helmets. I don't think it is wholly fair to characterize them strictly as a gimmick. For one thing, they are weighted so that the hook will ride with the eyes up, which you can't accomplish with most coneheads. Since they are easier to work with for spun deer hair heads as compared to barbell eyes, I can see an advantage here for certain patterns.
The helmets work great for something like a shenk sculpin, but you do have to be careful to leave enough space to push the helmet on after the fly is finished. The eyes are a pain in the *** to handle and attach to the helmets. I can't imagine the eyes matter to the fish, but people do like them.
I haven't fished extensively with the flies I've tied using these, but you can tie some nice looking imitations. I expect to use them more in the next 2-3 months, since I tend to fish streamers very near the bottom during the winter but not so much during other times of the year.
I doubt the results are any more or less effective where catching fish is concerned, but I can see why some tiers would like them.