In the year and a half I've had the SQ2 I've put 350 hours on her, nearly all of it off-airport in all kinds of weight configurations from full fuel two persons and gear, to just me and light on fuel. In that same time period I've put a couple hundred hours on the 185. If I could put slats on the 185 I would, although they would be of a design I could lock down from within the cockpit for cruise.
Cruise is the only flight envelope that Mackey slats don't improve, in fact they slow the aircraft. Some guys drill holes in the slats/brackets so they can "pin" the slats closed for long cross country flights. I'm considering that for my trip back to Alaska in May. Bruce at Backcountry Super Cubs is working on a manually deployable slat system with a lever similar to a flap handle. The prototype I saw had two positions, closed and fully open. It will obviously weigh more then the Mackey slats.
More important to me then the STOL improvement with Mackey slats, is the safety improvement. I can rudder turn as much as I want, as slow as she'll fly, without risk of stalling a wing or spinning in. When I'm close to the ground, say following a river, where I don't have the height to safely bank in turns I just step on the rudder as much as I need to make the turn while keeping the wings level.
Or if I'm higher and I've got side canyons coming in on a turn with high winds that could flip me over on my back again I just step on the rudder, keeping the wing down so I don't get flipped.
There is no portion of a flight where I feel the slats working or not working, meaning what they do and when they do it is imperceptible to the pilot. As far as takeoffs or landings with gusty winds, crosswinds, or gusty crosswinds, what the slats will or won't do for that aspect of the flight is not a consideration for me. What is a consideration, and the major one, is how much wing underside I'm willing to expose.
Because my SQ2 stall speed is 26mph if I've got a crosswind landing and have the runway width then of course I going to land as much as I can into the wind. If the runway is narrow then I'm landing just like I would in the 185, wing down on one wheel, tail as high as needed to keep from being gusted back into the air.
Mackey slats keep the wind on the wing (so to speak), which does allow crazy high angle of attack landings and takeoffs, but the plane can takeoff and land with the same profile as a Super Cub as well. It's up to the pilot and of course more importantly up to the specific situation. But even here the slats provide a huge margin of safety cause if suddenly you were inadvertently gusted up or the wind dropped out from under you and you pulled back on the stick to try and catch the plane before it dropped in, the slats open and keep what wind you have over the wing.