They are not equipped with a firm mechanical connection comparable to standard clipless pedals. The force of the magnets can be impacted by several factors including magnet size, dirt, wear, and direction of force applied. Unintendedly disconnecting from the pedals is possible at any time.
I guess they are a great idea if you want to buy and wear cycling shoes without the benefit of foot retention. In other words, they are as useful as a fart in a phone booth.