The seat height is not too low. Most people can get seated and get back up without too much trouble.
The seat back angle is fairly upright. Leaning back is good for racing but most riders prefer to be more upright.
They accommodate a wide range of rider sizes and are easy to adjust.
The frame geometry leaves room to get on and off the trike.
The frames are sturdy (and fairly heavy).
The mechanical and electrical components are high quality. (They still need maintenance!)
