Traditionally, I've been vehemently against laser use in almost all situations, with one of the big exceptions being training use. But the last few months, I've softened up on them a bit. I still do not own a laser, but may consider picking one up in the future.
Some things to keep in mind if you are going to use a laser.
-Don't rely on the laser. When you practice/train, spend more time with your irons than your laser, but make sure you're working both.
-The laser is a tool. Just like any other accessory. Like any tool, it has times when it works really well, and other times when you'd be crazy to use it. I have a hammer in my tool box. But when I change the oil in my car, there are better tools to use. Know when to use the laser and when not to.
-Don't let your fundamentals slip (sight alignment, sight picture) slip just because you have an "easier" sighting method.
-Know the limitations of the laser. Know when it works the best. Know when it's useless.
I'm a practitioner of the K.I.S.S. (Keep It Simple Stupid) method of training, shooting, carrying, etc. Lasers add complexity to your system. Anytime you add complexity, you are adding a point of failure. Sometimes, the failure isn't noticeable or doesn't effect the end result. Other times, it could mean the difference between life and death. It's up to the user to weigh whether the additional complexity is worth the point of failure. Keep in mind that in a gun fight, if you were planning to use your laser and for some reason it doesn't work, it might not be as easy as just transitioning to your irons. You may lose a second or two, and that second or two could mean the difference. Is this likely? Not really. But then again, it's unlikely you'll ever have to shoot in self defense in your life also. So we're already dealing with low odds.
Having said this, I am currently (well, I will be in a few months anyway) in the market for a church gun. Basically, I'd like to pick up small single stack 9mm that I can easily conceal in my church clothes. I'm seriously considering a laser for it. Why? Because typically small guns have crappy sights. I'd like to be able to hit what I'm shooting at.