So many times I could have used one. Everyday light duty B&D drill has
one built in. It can and has been handy. But I'd like to get a decent
one. Trouble is, even the ones that push say $75 (I know they can cost
hundreds) have an accuracy spec I think sucks for a laser. If I recall,
lasers are coherent light and are pretty darn straight. Light travels
straight unless it's bent or distorted and laser light doesn't disburse
in general. Also if I recall, the intensity and directness of laser light
depends a lot on the mirrors generating the exit beam.

How the hell did I get off on that tangent...?

Anyway, I see accuracy of +/- like 1/2" in 100'. Saw a $35 Sears brand
one today (not self leveling) that was +/- 1/2" in 30 ft. Crimus!, I can
almost do better than that eyeballing.

What exactly is the "accuracy" spec?

For a self leveling one, does this mean the two endpoints at the spec
distance and be off up or down by 1/2"?

How about one that is not self leveling...basically shooting a straight
line. Does it mean the beam can be bowed +/- 1/2" at any point alone the
line?