I've got one on my P3at Keltec and it was just about on the money out of the box. Took about 5 minutes to install and adds zero to the weight and comfort of the pistol in my pocket. It is as slick as any laser could possibly be. I've had it on for about 3 months, now, and the batteries are still going strong, too.
The laser on these little pocket pistols is a fantastic addition for a few reaons.
1) They allow you to align the pistol on your target from ANY position you hold the pistol in. That allows you to put the muzzle on the target holding from the waist or even under a table or on the floor. There is no requirement that you hold in the traditional method to sight along the barrel. That right there is quite an asset. For a carry piece where you may be in a situation that doesn't allow a good traditional stance or where you don't have the time to set up, this could become a life-saving and welcome addition.
2) The laser doesn't make you a better shot, however. You still have to learn good trigger dicipline because pulling the trigger on these pocket rockets is not for the faint of heart. They are all DAO and have a very heavy pull and that tends to pull you off target. Still, by putting the dot on your target, you can learn good trigger dicipline which will make you more accurate eventually. It is easier than trying to site down those non-existant sights on these models.
3) The biggest thing about a laser is the intimidation factor that they bring to the table. There is a DVD that you can get with your laser that talks about that feature. If there is a red dot on the badguys chest, chances are they will think twice about the size of the pistol pointed at them. This is not a small, insignificant issue, either. That laser dot is very bright and a badguy will most certainly think twice about continuing his attack with it on them. And, if he doesn't, then you're most probably going to hit center mass anyway. At least you can see where the bullet is supposed to go but that gets back to #2. Learn to practice with the laser, relying on it more than using the sights. Let's face it, these little pistols are instinctive shooters anyway so the laser give you the confidence that you're on target, especially at nominal ranges.
Hope that helps a bit. I love mine and another buddy just bought the same unit for his Ruger which is a clone of the Keltec. It also helps with dry fire practice in my office when I'm bored
Rome