I have bought several, and all but one turned out fine.
The latest acquisition had some issues. The seller was working on consignment for a friend of his. The seller had a good rating, with many transactions.
Problem was, there were issues with the gun that I wasn't savvy enough to notice on initial inspection, and by the time a gunsmith friend of mine looked it over, it was too late to attempt a return.
Used, WWII issue Colt 1911. I knew it had been reblued, and had newer grips, but that didn't bother me. It arrived with a National Match barrel and bushing, and that itself wasn't a concern - the bluing and grips had already tanked collector value, and I had not paid a collector price, I had paid a shooter price.
However, it turned out that whoever did that barrel installation didn't fit the barrel quite right. Also, the person or persons had ground out the feed ramp in the frame, so that the .030 jump from ramp to barrel ramp was non-existent.
The gun worked ok with ball, but would not feed hollowpoints, due to the things that had been done to it.
Bob Hunter improved things somewhat (I'm lucky enough to live a half hour from Bob), and now the gun will run HP so long as I load ball as the last round in the magazine. Due to the metal removed from the ramp, he could only mill the barrel ramp so much without risking case support.
So, this was a "live and learn" for me. A quick once-over, then a range test with ball ammo, may not be sufficient for finding deeper problems. If you buy anything other than NIB, a gunsmith inspection might not be a bad idea, unless you really know what you are doing.
I'm a good shooter, but I am not much of a smith.