For defensive purposes I don't see how the laser is all that useful. If you are in a situation where the flying defecation has impacted the rotating air motivator the adrenaline levels are going to be through the roof, the heartbeat will be sky high, physiological flight/fight response will be pulling blood from extremities, and tunnel vision will be closing in. Hitting a button for the laser and the additional mental processes associated with seeing the red dot will either not happen (best case) or will make you slower (which can get you killed).
On the other side.... Lasers are a useful tool for dry-fire exercises and can be fun at the range. There is also the potential psychological impact they could potentially make on an intruder in a dark room if you catch him/her by surprise. They are also immensely useful in keeping cats and dogs occupied.
My suggestion is that if you are buying the gun for self/home defense, skip the laser and put that money into buying more quality in the gun. If buying it to have some fun, knock yourself out.
Quis custodiet ipsos custodes? (Who watches the watchers?) --"Satires", Juvenal (Roman poet)