I have a set of the Claw. Haven't used them much, at least not in big winds. I'm told (and the instructions are clear on this, if you read them) that they have to be right under the tiedown rings to work right.
I've ordered a set of the Fly-Ties as well. I'm hoping, if I can borrow a strain gauge, to do a pull test on both sets.
According to some folks, there were some failures of the Claw at Sentimental Journey, where they had huge winds, and rain. I suspect that wet ground isn't going to hold as well as dry either, and ever type of ground is going to be different.
I carry a set of Duckbill Earth Anchors with me when I travel. These require a drive rod (piece of rebar works fine) and a serious hammer or hatchet to put them in, but they work. I use them as permanent tiedowns nad have for years. Unfortunately, if you want to get them out, you'll have to dig them out, which might not make you popular with the Poberezny's, if you use em at OSH. The guy with the lawn mower wouldn't like you much either.
On the other hand, losing your plane isn't such a sweet deal either.
Any of the other screw type anchors are, to me, either a huge pain in the arse, or good only for tying out your Bichon Friese.
MTV