I've often thought about getting a set of these for various snubbies, not for the "dot in the dark" aspect, but as a training aid (like Mike and Jeff have talked about). Snubby j-frame and SP-101 sights could be a little more generous, and the pistols seem to me to be more difficult to shoot accurately than a full-size, due to the smaller grip frame (j-frame) or heavier trigger (SP). The laser could be a real benefit in target practice, because those things really jump around if you're not perfectly still. The j-frame is the gun I shoot least well (the only one that I can't consistently group into an inch at 30 feet), so it's the only one I'd consider buying laser grips for.
There are only two reasons I haven't bought them. First is price: I can always find something better to do with $188 (a good price for the laser grips). Second is the fact that . . . it's a snubby, it's for concealed use. Why put a bigger grip on than is absolutely necessary? I'm a guy who's sanded down the Uncle Mike's rubber boot grips on his 940 to make them fit his hand better - grip fit is really important when trying to shoot a jumpy 9x19 j-frame accurately. And grip size is important for pocket carry. And you should practice with the grip you're going to carry. I know CT has the two styles of j-frame grips, but they're both larger than the boot grips.
I think laser grips'd be great for training on a snubby, but I never have been able to convince myself to take the plunge.