Stay away from the ortho belt and go with the 4500T model if you must have a Keys. If you must have a Keys treadmill, I've got a dead tree in my yard. If you pay me $1000, I'll let you remove and haul away the tree. The tree company wants me to pay $400 to have it removed, but I figure I can find a sucker that bought a Keys machine to pay me to do it.
Decent effort but there are some other good options on the market that provide more value and better build quality. When you consider no warranty and the company is not around, you've got all the ingredients for a disaster.