I disagree with most points presented.
I shot 50 rounds yesterday for Police Qualifications. My dept issued us the LaserMax guide-rod for the Glock 21. I have heard all of the excuses for not using them presented in these posts and some that haven't been posted.
While we were given the option to use them or not, I chose to keep mine. I have shot thousands of rounds with it with no problems whatsoever. I have never had mine turn on or off in the holster. I like it and I will continue to use it.
As for looking at the target, in a combat situation at normal defensive ranges, if you are taking the time to look at your front sight you are taking too long. If someone that knows how to shoot is on the other end, it is more than likely that you will takes hits and possibly even die.
Most of the guys that made excuse for not using them are not "gun" guys. Some of them have no mechanical inclinations what so ever. Some of these dudes have a hard time taking their duty belt off or taking their gun apart for cleaning. It was no surprise to me that some of them moaned and groaned about the guide rod laser.
As for disassembly, I have never noticed the difference. As for POI, if you put the small red assembly dot where it is supposed to go, you POI will be right on the money.
As for turning itself on or off, I suppose that is an issue with the particular brand of holster that its in. In my case, I use a Safariland Level III which is held secure by three different methods and have yet to have an issue.
As for FTF,FTE or FTB I have never had an issue with any of them.
Although I don't doubt that some people have issues with them, I have been fortunate to not have any. About the only negative that I can think of is that after several hundred rounds fired, I thought that the batteries were getting weak. When I broke the gun down for cleaning, I noticed that the lens was pretty filthy with carbon and burnt powder residue. A quick wipe with a rag had the beam showing strong again.
I like them and I continue to carry it on my duty gun, the G21. At night time that laser can be seen quite a ways off.
It is also quite fun to harass cats or dogs with.
As with any laser, I don't think that its the perfect tool for self defense, but it is a tool that can be used effectively and any tool that might add an advantage is a good tool.
Also, the option of turning it on or off is a good one,escpecially for someone may not need to telegraph their intentions.