If it is a good quality scope, factory service or equivalent is available, price is right, and you are comfortable with the seller's integrity, I would do it. I have sent a few scopes in for factory servicing (for other people) and they came back like new. If you can save some $$ that way, I think it is fine. There are occasionally such good bargains available when models change, etc.; however, sometimes it's hard to reconcile buying used. I guess you just have to judge each case on its own merits.