Quickshift is really a nice feature... got used to it when i first got my 18-55mm DA II kit lens... and then got the first 55-300mm... and then again with the 18-135mm!
When handling other peoples cameras I instinctively try to do a quick-shift focus when i simply can't
Oh, and that damaged DA L in the other thread... that looks like damage from seriously knocking the lens off the body... something like, say you're walking (reasonably fast paced) with the camera dangling off the side of your body - the lens is facing outwards.. then whack, you hit a pole/wall/doorframe/etc... since it's two of the flanges (that the name for them?) snapped off. although a whack would show more damage to the barrel of the lens... could also be weight being pressed down on the lens so the flanges break..
Essentially it seems like severe mistreatment of the lens to cause that sort of damage... not really an argument in plastic vs metal mount... you could probably cause similar damage to the flanges on a metal mount if you had a serious mishap/mistreatment of the lens too.