Dave, that's the way I hold it too - in fact AFAIK that's pretty much the standard pick grip.
Problems with pick slippage are why I use the big triangular Jim Dunlop ones. As basic physics tells you, frictional force is proportional to pressure and surface area. More surface area, less pressure needed for the same amount of friction.
As far as I can see, this isn't replacing the flatpick. Instead, it's an improved fingerpick. Standard fingerpicks are a complete non-starter for me - they only work when picking up (closing the finger), and any attempt to pick or strum down (opening the finger) will always trap the string between finger and pick because of the shape of the pick. Alaska Piks were much better, but they didn't grip my fingers perfectly and didn't give that much improvement over nails. These look like they might be an interesting experiment though.