Mixed results, according to Craig Peterson of RadarTest.com. [As an aside, although Mr. Peterson is a well published tester of police radar and laser countermeasures, I question his impartiality in light of some of his radar detector reviews, so I'm somewhat reluctant to cite his work.]

Personally, I have my doubts about the effectiveness of laser jammers. I'm even more skeptical of radar jammers, which might better be branded as electronic snake oil.

One factor you should definitely consider is the relative scarcity of laser units in the United States. They are still much more expensive than radar units, so only a fraction of police traffic enforcement vehicles are equipped with laser instead of radar. Depending on your jurisdiction, I'd be skeptical of the utility of a laser jammer.

I have a chronic lead foot, so believe me, avoiding traffic tickets is critically important to me. My weapon of choice is the Valentine1 radar/laser detector. It is head and shoulders above the competition in my personal experience for two reasons: (1) it's incredible combination of accuracy and range; and (2) it's unique directional arrows that make it the only detector on the market to tell you from what direction you are being clocked. And Car and Driver rates it number one in a landslide as well (97 points out of a possible 100 to the second place Escort's 73). I would strongly urge you to consider spending your money on a Valentine1 before worrying about a jammer.

As an aside, a good source of information for would-be speeders is the National Motorist Organization website.