The Glock 23 is a typical boring Glock. It's utterly reliable, lightweight, soft shooting, more accurate than 99% of the people that shoot it, and extremely simple in design and function. I've had this one for a few months now and have just over 500 rounds through it and here's what I've found.
-Reliable (0 malfunctions of any kind; with and without tac light attached)
-Accurate (more accurate than I am)
-Durable (I have a Gen2 23 with thousands of rounds through it and it's still going strong)
-Easy to maintain
-TONS of aftermarket support
-Accepts 13, 15, and 22 round factory magazines
-Small and light enough to carry but holds 13+1
-Glock's customer service is second to none
-Cheap replacement parts, should you ever need them
-Low Bore Axis resulting in a relatively soft shooting gun
-Easily modified to fit the shooters' preferences
-Requires very little cleaning/lubrication to run reliably
-I like the Gen4 grip texture; especially in the 40S&W guns
-It's had consistent ejection with all ammo
-I'm not a fan of the factory plastic sights
-Comes with a serrated trigger due to import rules (easy swap)
-I'm not a fan of the Gen4 backstrap system. It's never failed me but the system used by other manufactures integrates more seamlessly with the firearm than the Glock system
Here's a video with some shooting from the 12m line, a table top review and discussion, and a chronograph test with some popular defensive loads.
Gen4 Glock 23 HD Video Review Link
Winchester Ranger 135gr JHPs: 1124 fps, 379 ft/lbs energy
Federal HST 180gr JHPs: 997 fps, 397 ft/lbs energy
Federal HST 165gr JHPs: 1051 fps, 405 ft/lbs energy
In summary, it's tough to go wrong with a Glock 23. It's adaptable to most uses (duty, HD, concealed carry, ect...), can be easily converted to 9mm for cheaper practice, it's adaptable to the shooters hands, and most importantly is utterly reliable.