I'm in the skeptical camp on this one as well, for a couple of the previously described reasons by ReverseApacheMaster and Camping57. This is not a new concept. There are a few studies out there which discredit this method. I just never favorited them in my browser to repost them here.
Also, I wouldn't want distilled spirits added to my beer, just as I wouldn't want beer added to my distilling spirits. A 1/3 to 1/2 cup or so is okay for something like rum soaked vanilla beans in a dark beer, but you'd be using more spirits than that for attempting to mimic dryhopping in a pale IPA. Even so, you cannot say that your 1 pint of spirits with 1 oz. of dryhops will offer more aroma in the end vs. no spirits via a traditional dryhop with say 3 oz. The amount of extraction and sustained aroma is not greater with the tincture method and no money or time is really saved in the end.