The male "X" on the pedal interfacing with the female "X" on the shoe probably has as much (or more) to do with keeping one's foot securely on the pedal as the magnet itself. It looks interesting. One concern is that it looks like you wouldn't have much (if any) lateral float and, unlike clipless pedals, you can't adjust the position of the "X" on the shoe to get the angle right.

I'd like to try 'em but I ain't gonna buy 'em.