I bought an Essex Silverline on Ebay 3 months ago for $250 with some hopes of it working after reading on the web site that, "The design allows the DIYer to accomplish the work of a rotary polisher without knowing how to run one!" Well, my 175 works great on carpets so I thought it was worth a shot. If it didn't work I could rent it out for floor work.
http://www.essex-silver-line.com/sl1218.html
The first time I used the unit was on a dense plush with a glad and it pulled the junk off of the top but was too hard to control. The handle doesn’t lock, it was way too heavy at 125#, and glads don't cover the entire drive pad. To top it off, it quit running. I thought I overloaded the machine the way it was digging in and cleaning so I  hit the reset button and still nothing. HWE it was to finish. Found a wire came loose on the switch so a simple push on the connector and been working flawlessly since.
Next, at home I tried it on my test area rug and it danced the rug all over the floor with a bath towel and glad pad. It did better with a fiber plus because of the thickness and less grab but danced a little too.  Tried it then on the only installed carpet I have in the house and shook it around too. My thought were that I would have to carry around stretching tools to repair the damage it could do so it was off to the corner to sit until I bought a square pad to do my kitchen floor. For the intended purpose tile maintenance, it did an exceptional job, much easier to control, got the corners, and didn't sling anything. In all,  my experiment demonstrated that OP can clean what you thought was clean, so, time to save money to buy a real OP.
About a month ago I saw the TerryTowel website, watched all of the videos. I notice that the differences in machines are the handle locks, the handle is attached at the center of gravity, there are wheels that touch the ground, and is lighter in weight. There is no mention of glides available.  I think on the right carpeting like CGD the fixed square plate can be useful because it does dig in and cleans great but I don't have any real OP experience to compare my experiments to a real OP. I'm a little hesitant to try it on a customers carpet with cotton or a glad because I don't have the resources to buy them a new one if I'm wrong plus it's too heavy to drag around for encapping with a fiberplus.

I see tip blooming on nylon carpets as being a likely serious issue with a machine that doesn't turn.  I'd be very careful if you're going to try using it on nylon carpets.

i think clark builds those machines for him. he had a bunch of vids on youtube a few yrs back and after viewing i thought it'd take  a week to clean a home full of carpet   

Clark does make the machines, the smaller  50lb machines have a 1/4 inch fixed orbit and are slower, they clean well but not as good as a heaver larger random orbit machine like the Defender or CX.
The small towel machine is what I started op cleaning with years ago and it cleaned as well as what was available back then.
The larger towel machines which I believe is what Teritowel is using now, weigh I think between 70 to 80 pounds, I had a couple of these in the past, they have a 1/2 in. fixed orbit and will clean as well as any op machine, I've tested them side by side with other brand op machines.
The fixed orbit digs in better than the round random orbit machines which allows it to clean as well with only a 1/2 in orbit but also makes it clean slower.
You can use glider with these machines or synthetic pads or towels to move faster.

So that means if Clark makes them they are way overpriced.