I don't have any first hand experience with the 4th Gen Glocks but I've been doing some re-search on them.
It sounds like the .40cal Glocks are running just fine while the 9mm's have had a some issues. But there have also been some reports back that "their" 9mm glock has been trouble free.
If your interested in the Gen 4 Glock 23 for the reasons you stated. I'd feel comfortable enough to get one with the re-search I've done. But as DJniner has mentioned threads on other the 3rd Gen Glocks have been around for quite a while and have a very good reputation.