Just got back from the range, where I fired my new shiny Gen 4 Glock 27 for the first time. (Just picked it up yesterday).
To be honest, I'm quite shocked (in a good way). I've expended thousands of rounds through my Glock 17, and I'm already more accurate with the Glock 27, after shooting just 2 magazines (18 rounds total).
The image below is my target from today. The top target was 2 magazines on my Glock 27, at 21 ft.
I talked to a guy at the range who said it's common for people to shoot better with the subcompacts (for Glocks anyways).
There's a million reviews out there on the G27, but I'll just say it felt great, and performed flawlessly. It'll take me a while to get the first 5000 rounds through it, but, like I have always done with my Glock 17, I keep a log of how many rounds, type of ammo, and any type of malfunction. I'll keep you all posted.
By the way, here is the bench I was on today. Had my G17, G27, Ruger LCP, and my friend had his Mac 10 and a Springfield XD9. Lot's of fun!