If you like the TR500, put the extra dough with it and get this TR1000 model. The difference in motor, belt, etc. are well worth the extra scratch. The base design of this unit is quite good.
Some cheaper components like the motor and electronics are offset by the price and its ability to fit into a small area. Ideal for those who want to save space.
I bought this product and been using it for a year. The frame is poorly designed since it is a welding frame. I will recommend going for any TR treadmills above the 1000 model.