Hi dw,
I have worked very closely with the Skiers Edge company for many years. The owner/developer of the company is a friend and ski student of mine, and I am happy to say that I have had some input over the years into the development of the project. If you have any of the videos that come with the product, you will see me and my wife skiing and talking about it.
If you contact the company, they have a fair amount of material on using the machine for rehab, more often related to knee surgeries.
Unfortunately, I was away from the home where I have my machine for the first five months after surgery, and so I did not get on it until the five month point. At that point, I found it to be a terrific daily rehab tool, and a major part of my training before getting back on skis at six months. In part because of the machine, on my first day back on skis, I was able to spend six solid hours skiing steep powder and crud; not bad for a first day back.
If you are lucky enough to have access to a machine sooner than I did, I would offer these thoughts;
1. Use the support bar rather than poles, if you have one. If you do not have one, you might consider ordering one. It is suggested for rehab, since it virtually eliminates the chance of losing your balance and having an awkward dismount.
2. The older machines (Classic model) had a little more impact at the ends than the newer machines (I use the "Big Mountain" model), which I do not believe involve much impact. I would consult your doctors protocol when deciding when to start using the machine. If you have a cooperative doctor who is not familiar with the machines, you could ask him to go to the web site and watch them in action.
3. If you or your doctor have concerns about crossing the mid-line, you could change the tension settings so that the lateral travel stops sooner.
Bottom line, I feel that it is spectacular rehab and training tool after resurfacing, but I would consult your doctor about when to get started on it, and I would consider the above suggestions.
John