A budget unit that can work if you take very good care of it. Just keep in mind that it will eventually break down.
The warranty on the Proform 6.0 ZT is very bad. Parts and labor are covered for 90 days, while the motor is covered for 5 years. As you can see by the manufacturer's lack of willingness to provide decent coverage, we aren't the only ones who project this treadmill will break down rather quickly.