I've only bought three guns so far -- one used (S&W Model 60), and two new (Mossberg 500 and Springfield 1911). I haven't had any trouble with any of them. The S&W was on sale at a local gun shop with a sterling reputation (with the BBB and in the gun community), and had originally been sold new by the store, so I wasn't concerned. I've now had it for a year, and the only issues I discovered were that the original owner needed to learn how to clean a revolver (black *ICK* on my hands when I used Hoppes #9 on it) and the adjustable sights were not aligned well (easily fixed with a pair of pliers and a bore sighter).
In general, I wouldn't buy a gun that had been used hard. If it's in good shape, the brand and overall quality are far more important than whether it is new or used.
In general, I wouldn't buy a gun that had been used hard. If it's in good shape, the brand and overall quality are far more important than whether it is new or used.