Sam:
Since the replacements are metal and plastic, they do not have the extremes of range of motion of original human anatomy. However, they are pretty good -- and far better than a weakened, arthritic, diseased, and deteriorated pre-surgery shoulder.
There are precautions that need to be followed after the replacement. The danger of damaging the implant is always present, and premature wearing out of the implant is something to be avoided. So, it is best to avoid things like heavy bench presses, heavy recoiling rifles, punching a heavy bag, throwing a fastball, etc. -- Simply being as strong as possible without large shock loads or overloading the plastic glenoid cup too much is the order of the day.
Before the surgery, my shoulder joint was so worn out that I could not do much, so the after-implant precautions are still better than before the surgery -- but not as good as my shoulders were 20 years ago when I was a bit of a fitness beast.