When I see used machines on Craigslist, I am sometimes tempted, but I always end up deciding if I'm going to spend a significant amount of money, I want a warranty and some place to go if there's a problem. I don't think I'd spend a lot buying from a private party, but I guess it depends on your disposable income.
To the original poster, maybe find out what trade-in value you can get, and then go from there...