I started with a lot of CG presses at the first of this year. My lockout was pretty shabby and needed work. It brought my tri's up to par pretty fast, and now I am just benching heavier and doing direct ancillary work for the tri's.
One thing I notice though, if I let the bar drift too far down the press turns into a shoulder/ bicep move instead of a pressing motion. Probably just my lack of control and stronger bis wanting to take the load, but it was very annoying when trying to get those tri's in shape!