I agree with Candace. Check the homequiltingsystems group for comments. It seems as if the majority are happy with the end result, but a few have had problems. If you are one of the unhappy ones, there is really no recourse as the machines are not guaranteed (as far as I can tell). All of the risk is yours.
Personally, I would prefer to buy an already-stretched machine so I could try it out and make sure it works before purchasing.