One thing I notice at my gym is that a lot of people when either doing military press with a bar or doing shoulder presses with DBs use the backrest. Heck I do sometimes. It means you can do higher weights usually.
However one thing I notice is that people's form goes out of the window since they can use the backrest to push against and move to a slightly "inclined" position and not really isolating the shoulders.
Personally I like to do shoulder exercises without the backrest - sure with the backrest I can military press over 90kg, but without it drops significantly, however I get a MUCH better work out IMO. Similarly with arnies, I just make sure I tuck my legs under the bench for support, lock my core and lift in a slow controlled manner - I get so much more of a pump doing that.
I also do standing shoulder press (I'm not sure of it's official name) which obviously means you can't use a back rest. :p
Lastly, I see some guys bring the bar behind the neck without a spotter :/ I seriously worry about some people sometimes. I tend to keep away from the back of the neck with the bar tend to go to the front - I bruised a vertebra (playing rugby) really badly on my lower neck, and I'd rather not do it again! :p
Thoughts?

