While it's true that live fire is quite different, it's also true that doing any action "really slow" allows your body to retain muscle memory. There is an advantage to perfecting your slow dry fire practice. I don't shoot a Glock so I use a Laserlyte Laser Pulser (http://www.buy.com/prod/laserlyte-9m...ngId=207245993). They have them in most calibers, but 9mm linked here. The advantage of the laser dry fire training is not only can you see where your shot would land, but whether you were moving the gun during the shot (You will see a trail or line instead of a dot.).
The King of Dry Fire is Steve Anderson, and he has some dry-fire training manuals you can purchase for reasonable price and he conducts competition training classes. http://www.andersonshooting.com/. His dry-fire drills actually start out with indexing the sight without pulling the trigger. He does have you do other drills pulling the trigger, but his emphasis is on quick draw and index, or target transition and index the sight. Getting sights on target quickly is treated as a separate component.
I own both of Steve's books and I highly recommend them.
CC