Like most other things in life, this decision is based on the combination of your expectations, the probability of trouble, and your ability & willingness to deal with it. I and others have bought and sold on HB without a problem - the key is to do your homework on the object in question and (more importantly) on the seller. Knowledge is the key to estimating the probability of a problem.
If you're a perfectionist, you probably shouldn't buy from a slob - one person's patina is another's damage. If you're buying used because you can't afford the same item new, you need some cash reserves to deal with failures. The purchase price is not the total cost of ownership. You need to know about age, how hard it was used, its maintenance & repair needs & history, etc to estimate that probability of unexpected expense. And you need to adhere to the time-honored principle that "if it wasn't documented, it wasn't done".
And even if you buy an accurately described, beautiful, well maintained, lightly used machine from an honest seller, there's a small but real risk of failure through no fault of buyer or seller. If all this makes sense to you, you like the machine, and you can live with the deal, you're likely to be happy. If any of the above has you worried, you probably should buy new or from a dealer who offers a warranty & return privileges.
I hope that helps - good luck!! (PS: hope is a lousy business plan. If you don't know what you're doing, don't just jump in and hope for the best - the probability of disappointment is high.)