the quick focus feature is quite useful if you need to and know how to use it. it gives you the full control of your focusing between AF and manual correction. When you half-press your trigger to lock your focus, then it give u the extra feature to be able to make a manual correction to the focus before you release the trigger.
the other lenses w/o quick focus is then troublesome. When your half-press to lock your focus, you may need to re-engage your focus again to get another focusing point. But with the quick focus on DA, you can use 2 finger to turn the ring and get it right without re-engaging your AF. Its a hybrid feature, where you instantly have the manual focus feature when you need it in AF.
so far, i don't see anything wrong or unreliable with it. Infact, I find pentax way of doing this innovative. The other 3rd party, C and N lenses don't seems have this feature. (not that i know of).
many forum users dislike the focusing ring? ai ya, where are you reading them from? from people like you who don't understand it? it is not very nice you post remark like slack when you didn't completely understand it.
cheerss..