|-factory boresighting not adequate, nor adjustable.
-pulsing effect (intended to make it easier to acquire) EXTREMELY annoying. makes this laser useless for dry-fire trigger-pull practice, as well, as the pulsing makes it difficult to see small movements.
-odd activation method makes it difficult to activate/deactivate in a tactical situation (I.E. avoiding telegraphing your presence/location by turning off laser when not actually aiming at something)
-MOST IMPORTANT: it broke the first time I took it to the range. wouldn't shut off, except when removed from the gun or when the slide was locked back.