Their automatic uses centrifugal force to engage second gear. So another set of pawls would have to be added, and second would have to disengage somehow, so I don't think a 3 speed auto will show up anytime soon. The 3 speed that uses input from the front wheel to electronically shift is probably the closest to an auto 3.
The 3 speed kickback would have to be your only bike to get used to it. The 3 speed, from what the write up says, would not downshift back to second from third, you would have to tap the brakes, dropping it into first, then up shift to get second. That would be the hardest part to get used to, but with practice would probably be second nature.