I have CTC-installed grips on my carry gun, a Glock 26. I love them and would not want a carry gun that did not have them.
Most of the posts above are absolutely spot-on: these puppies are cool, there's definitely some good benefits to using them properly, and they really help a lot when shooting in low light. And -- it is not enough to install them. You have to train yourself to use them to best advantage.
Laser grips absolutely will not fix poor shooting techniques. They will not improve your trigger pull, or reduce your flinch, or anything like that. They are simply an alternative sighting technique which works better than anything else in certain, fairly narrow circumstances.
Several people have mentioned the laser dot "jumping around" on the target. Yep, the dot does that. It does that because we're human and it is impossible to hold the dot still with 100% success. Part of training with a laser grip is learning to accept that really small wobble, and pull the trigger smoothly anyway. That wobble is exactly the same size as your wobble zone when you look at your front sight, by the way. Learning to hold your firearm as steady as you can, accepting the wobble while pulling the trigger smoothly, is one of the secrets of good shooting. If you try to "snatch" the brief, magic moment when the sight wanders across the exact center of the bullseye, your shot will often go low. If instead you accept the wobble, you know that it will fall somewhere within that very small wobble zone -- and the wobble zone is much closer to the bullseye than your snatched shot will ever be. A laser can be a useful training aid to teach this type of lesson, because it is very easy to illustrate using the laser and relatively difficult to explain without the laser as a visual aid.
All that said: they don't make laser grips for the XD series. The other type of laser, LaserMax, is not the same as the CTC. I personally don't have a lot of experience with the LM types of lasers, but several serious folks I know who have tried them don't use them anymore for various reasons.
pax