Tam has a piece on what she considers the only two needed mods to the Generation 3 Glocks. Which reminded me of some personal history:
First pistol I bought for CCW was a Kimber Officer's Model 1911*. It had an extended thumb safety, and a standard slide lock and magazine release. Shot great, and one day I mentioned to a guy who worked at the range that I wanted to put on an extended slide lock(at that time I was still naive enough to believe what I read in the gun rags, and didn't yet know how they got that name). He said "Don't do that. Just practice with it. Put that extended on a carry pistol, and that's one more thing that can hang-up on stuff or get bumped at a bad time."
Thought about that a while, and decided he had the right idea. The stock lock stayed.
That caused me, when considering some reading insisting I needed a extended magazine release, to decide "I don't think so." Never regretted that decision.
Sometimes there are mods that are actually needed, like sights and/or a better mag release; the others are much like some fishing lures which are designed to catch fishermen more than fish.
*This was shortly before their prices went way up, and quite a while before their QC went down.