Unfortunately there is a lot of internet conjecture on this subject from people who don't shoot a whole lot. No offense intended.
I will second Zak's recommendation. Read Brian Enos' book. Read the section of focus, otherwise many folks here are talking past each other.
First and most important thing to do, seek out a good instructor. Then practice. Go shoot in action pistol games (IDPA or IPSC) They are just games, not tactical training, but they will teach you how to shoot with speed and accuracy, usually far far better than your average shooter.
It doesn't take many seconds to get into a shooting stance and access your sights. It takes a FRACTION of a second longer to use your sights, but with a massive increase in hit probability. As the range increases, this becomes even more true.
The only time for unsighted fire is at bad breath distance, or maybe if you are inside an elevator with the badguy.
For in the dark, that is what tritium sights and a good flashlight along with training and technique come in.
Lasers are fun, but for most folks, with proper training they can acquire the sights faster than they can find the bouncing dot on the target.