I'm subbing to this thread to see what others have to say. My Shoulders are definitely my weakness, yet through trial and error they're starting to come along.
I too was using the Smith for the reasons you said, but I'm now doing Standing Mil Presses in the Power Rack, safe and allows for full movement. Have you ever considered using the Power Rack? Just set the safety bars to just below where you stop your range of motion and there is your spotter. You can even move a bench in there to do them seated if you wish.