The most significant thing I can think of would be misalignment of the laser beam to the body of the laser. It's easy to check if this will be a problem - lay the laser in a V block of some sort, and rotate it with the beam on. If the beam stays in the one place, its colinear, but if it swings around in a cone, then it may not be good enough.
It depends how rough you want your alignment to be.
Al.