I don't have experience riding a trike but here is an interesting point or question.
The left wheel freewheels. The right wheel is on a coaster brake. So say a person is going downhill and is uneducated in the workings of this trike, and the person only apply the rear brakes - which in this case is only the right wheel brake.
Is the right rear brake only sufficient to stop a bike + rider + luggage going 12 mph without the application of the front brake?
Would the trike pull hard to make a right turn if only the right rear brake is applied? How much steering correction is needed?
I am a bit hesitant, I'll wait for the long term reviews.
Naturally, the safe way is to apply all the brakes all the time on a bike regardless of whether it is a 2, 3 or 4 wheels.
On the plus side of things, it seems to be a modular system - to a point. Even if Rad stops making it, you can add your own front drive system. This actually reassures me knowing I am not dependent on one company. Of course, if the rear drive breaks, one would still have a hard time if Rad stops making it but that's (not having a second source for all the parts) pretty standard I think for trikes.