Spiral mixers are efficient and effective dough mixers. They differ from the planetary (or KitchenAid) style in two very important ways.
First, there is an agitator arm in the center of the bowl that prevents the dough "riding" up the hook, getting stuck, forcing you to stop the machine and slide it back down.
Second, and most importantly, they are specialized; designed with one purpose in mind, kneading dough. To achieve that, the bowl rotates around a rotating, and fixed, dough hook.
Planetary mixers tend to have a very narrow capacity threshold, where if the dough is too small it won't come in contact or if it's too large the motor isn't powerful enough. With this machine, and it's powerful motor, we should be able to make batches of dough as small as 1 kilogram and as great as 8.
As a former kitchen professional, I would love to teach what I know of bread making to the MH community and enjoy the fruits of our collective labor!