I think that if you can look down the barrel like on a bolt gun or take off the upper on an AR and look down the barrel a laser bore sighter is not needed. I recently sighted in my AK and that was a pain because the sight was WAY off and I couldn't see down the barrel. If I have to do it again I will get the posterboard like someone else mentioned.
All the reviews of boresighters I have seen are 50/50. I would rather spend that boresighter money on ammo. Even if I am using more ammo like I did with my AK it was still enjoyable for me pulling that trigger.