I have over a dozen good quality "one handed" or "assisted open" knives and I wouldn't be without one. the same with carrying a Gerber multi tool because it is the easiest for me to opne with one hand. Just last night I was going to pour a bag a feed in a feed bin and I already had it up off the ground in one arm. I would have had to set it down and use two hands to open a knife to cut it open if I hadn't had an assisted opener.
This Christmas I "retired" my SOG FlashII, and replaced it with a Kershaw Whirlwind.