155 lb, 6' slow twitch climber here. I have owned one threadless 1" steel steerer'd bike. I see no gain, just bars that are nowhere near as simple to just raise ans lower, something I did many times a season as a racer. Winter miles - up going down as I came into form. Slammed for criteriums, up most of an inch for long races.

I took it for granted I could do this anywhere. (I've even been known to raise them when I was whacked just to get home.) Tools required: a 6 mm hex and something heavy. Crescent wrench, rock or big branch. Skill and attention level required: close to zero. Apply hex to tighten, don't honk on it. Done. (In general, slim quills are a lot easier to eyeball straight then threadless so that's also a plus, esp when you are stupid as happens late in rides.)

My one threadless will get threaded and quilled with a Nitto Pearl when it needs its next HS. I have a near sister bike with threaded and quills (yes, plural; two complete sets of cockpits and calipers. A 5 minute change takes it from a road bike to a climbing specialist. Takes fixed gear riding to new levels. I can do the change after riding myself stupid or just before I head out the door.

Ben