I still use them. It's hard to find a good bench for these so for the past while Ive been doing them in the Smith rack. The last time I was using a seated bench, the idiot I grabbed to spot me (non Smith) was day dreaming when I needed a spot and almost blew out a shoulder. I was ready to beat him when the weight was reracked.
It was mentioned, just dont go below parallel and you will be fine. I'm up to set of 8 for 185llbs and increasing. It is a solid exercise. After doing them you can perform this stretch..stand and place your knuckles on your hip, elbows bent, arm to the side, fingers pointing towards your back. Then take your free arm and pull straight forward at the elbow. This should stretch the rear part of the delt nicely.
Follow up with a rear delt exercise..one of my favorites..lay on your side on the bench. Using one arm, dumbell (15-25lbs), raise the dumbell from the floor--upwards. Keep the arm straight and thumbs down throughout the entire movement. Dont let the dumbell rest on the floor at the bottom of the movement to keep tension on the rear delt. The exercise is similar to a dual arm dumbell reverse flye but has better positioning to hit the rear delt better. It blows mine up.
All in all, my shoulders are strong, healthy, and flexible, and Ive always done behind the head barbell presses.