I only know from a friend that makes high end custom joinery for homes (stereo cabinets, custom bars, cabinets etc..

He's done a few boats and told me that the first boat he did drove him crazy until, for the most part, he threw the level away and started eyeballing everything except for the counter tops. Told me he eyeballed to taste. When he used a level most of the time it didn't look right.

That was before laser ones.