In my opinion, Glocks are great as is from the factory. However, some like to personalize them. Most of us I feel safe in saying have the OEM back plate on the slide and no problem at all.
All that I do to my Glocks is to have a 3.5 # connector put in to improve the trigger and install either night sights, fiber optic/night sights or fiber optic front sight. Oh, and for some reason that is probably just for looks I use the grip plugs to cover up the space left vacant in the butt of the weapon.