The machine is alright, but I found many people doing it like to cheat a few reps by using their body weight to bring the weight down, rather than focus on their tri's. Definitely agree with the people with weighted dips with a belt, but I don't recommend doing weighted dips every time.
If you work with your hands a lot. I used to work in the oil fields. And after a few years of working with my hands, and doing weighted dips, I have developed beginning of arthritis in both hands as well as beginning of carpal tunnel in both wrists.
This is also due to previous car accidents, and boxing experience, but just thought I would give my two cents.