gun searching!

The only thing I have heard of them is a few people were experiencing some issues with the new redesigned recoil spring. I believe that those issues have been worked out though. One other thing you may want to consider is, if you want to use a Guide Rod Laser. If you plan on making that purchase then you would need to stick with the Gen3 as they don't make it for the Gen4 as of yet.

Zombie Killer pretty much covered it. I prefer the Gen3s because of the initial Gen4 problems but as said I think they worked those out. The interchangeable backstraps are awesome.

Rest in this: If you get a Gen4 and something is not right, they will fix it for you. Its a new generation so they are working out kinks.

I have a 23 3rd Gen and love it.
i'm thinking about getting a glock in every gen

Haven't heard anything else, beyond what was previously stated. Although they are the new toys, think I will stay within the older ones, just personal preference.