her recovery from knee and ankle surgery and, though it has helped her a lot, I can really tell the difference in my body from the lack of it.
Arm weight machine exercises are pretty easy to replicate on it. The legs are less of a direct equivalence, but there are options with the total gym that get at the same muscles. Hams and quads are easy to get at. The leg pulley attachment lets you get to leg adduction and abduction, but those exercises are pretty awkward. I just do resistance bands for those muscles.
It's pretty easy to switch between exercises. You just snap on different attachments or raise and lower the body pad with pegs.
Where it really has an advantage over the strengthening machines in the gym is with stretching, again with the leg pulley attachment, especially of the legs and lower back.
I have a pretty basic model. It was @$400 three or four years ago. Just make sure you get the leg pulley (which is just a cord with an ankle strap). Also, the foot platform which comes with the machine was not tall enough. I'm 5'8" and it didn't allow me to do knee flexion without going past a 90 degree knee angle. I sprang for the $60 for the taller foot platform, and it was well worth it for knee health.