The Glock 23 continues to haunt me. As much as I try to hate it and prefer M&P's, 1911's, S&W 3rd Gens, I keep coming back to it.
Why? Because it is almost the perfect ALL AROUND size. Note: there are better range pistols, there are better CCW pistols but OVERALL the 23 can do it all.
Also, having dabbled in 9mm during the ammo crisis last year I have to admit that I prefer 40S&W (and, of course, the 10mm). Not that I don't feel safe with a good 9mm load - and there are lot's! And not platform -- in fact I am a HUGE fan of the M&P 9c, but I just prefer a 180gr and its thump.
But, why the Gen4? Well, I already have a Gen3 and I find the new grip texture to be really comfortable. And the SeeCamp-inspired dual recoil spring? Well, quite frankly it does work in my 27 and countless other implementations (Colt Defender, etc).
The finish worries me, but as long as the slide is Tenifer steel hardened, I am ok with it. Break in (as reputed on the internet) is not a big deal to me. You should put 300-500rds through a pistol before you deem it worthy to stake you life on any way. Besides, I have a Gen3 23 to rely on anyway.
I see a Gen4 Glock 23 in my near future.