Read quite a bit on these - they literally are a straight swap, and you can 'tuine' as much as most people need using the hand controller.
Seem like a god send to me - I like to keep things simple, and to have a control box that just goes in the same hole using all the same wires and plugs as the original one AND has a number of default programs seems too good to be true.
Nengun is trustworthy are they?