I buy mostly used Glocks, and have only had one I would consider slightly disappointing (not as accurate as I thought it should be); most other folks would have been happy with that one, as well.
Originally Posted by rumaco
The money I saved buying used vs. new-retail for the last 6 Glocks, paid for the next two I bought. Plenty of good advice above about selection; I'd add that if you simply pick a 9mm Glock that looks like it hasn't been modified, you're probably good-to-go and will be satisfied with the purchase.
Here's a photo of my "great satisfaction" (so far):
"Placement is power" -- seen in an article by Stephen A. Camp
(RIP, Mr. Camp; you will be remembered, and missed)