My edc is a spyderco delica. It didn't take too much practice till I can open it one handed and lightning quick. My Cuz has an assist knife (I forget the make) and it didn't seem to open any faster or require less dexterity to open than spydie. Though I wasn't practiced at it.
The lock backs do need a tad of maintenance to keep lint and dirt out for safe operation. I's not been a real pain to keep up tho.
I haven't seen anyone really explain the virtues of the assist. I'm looking forward to the remarks by those who have them and use daily.
Tom