I have had many used weapons that I trusted my life to.
Used doesnt mean sub quality, or beaten....it just means you arent the first one to pull the trigger.
I have had used pistols that were visably no different from a brand new one in the case.
I am looking at my G22 sitting in front of me right now....it was used when I got it...had maybe a box of ammo though it.....came clean and damn near perfect, barrel didnt even have scuff marks at the usual places where friction occurs during cycling!
Just shop carefully, be patient, and you can find great bargains on brand name weapons.
I actually try to buy used most of the time....it saves money, and most of the guns I own I have no reason to buy a brand new weapon.
If you are looking to build a match grade, precision target weapon, then yeah....you will want brand new, perfect parts.....if you are looking for a regular shooter, or even a CCW, used is fine....just stick with reputable brands and models.
(Here is another way to look at it......was your wife or girlfriend a virgin when you met her? How much difference did that make over time?)