Where I'm coming from - built ~80% of a Sonex airframe (from plans) and sold that project. Built another Sonex from plans, completed and flying for ~3 years now.
1. Build time - had about 1250 hours into it at first flight. Since then about 100 more hours with finish-ups, modifications, changing things. "From plans" = I bought the welded parts and pre-bent long sheet metal from Sonex, so it's not as "from plans" as one could possibly get, but I still hand cut every sheet and hammered out all the ribs. Kits can greatly reduce this number, and Sonex offers the option to use as much or as little of their kit parts and quick build options as you want to pay for.
2. Crosswinds? It's pretty robust, but still a tail dragger. So know what you're doing. Nothing wicked, tricky, or dangerous about the handling.
3. Longest leg I did was 1.5 hours each way. That's about all I wanted to sit in the seat. So no, it's not a great x-c machine for me, but I fly EXACTLY the Sonex mission - mostly solo, less than one hour, local area. So weights and capacities aren't an issue. What kind of flying do you really do?
4. Payload. Payload is just a trade. My Sonex came in at 660 lbs empty. Total payload is 490 lbs. Fuel can be up to 100 lbs of that payload. Trade off whatever is left for people in the seat. One nice thing about the 3300-powered Sonex is so long as it is within gross weight, it doesn't matter how the 490 lbs is traded between people and fuel. It runs out of gross weight before it's loaded out of cg. With the lighter-engined Sonex's, particularly the Jabiru 2200 option, it can go out of aft cg due to the lighter engine. That's probably one reason the gross weight is lower - to reduce the chance of loading out of aft cg. And since the fuel is forward of cg, as it burns off, cg moves aft. So one could take off in a lighter-engined Sonex and burn fuel to have to land out of cg. So with those, you need to pay attention.
5. As someone else said, turbulence is a function of wing loading. The Sonex is at around 11 lbs / ft^2, so a bit higher than even some of the 1320-pound LSA's, so it's still a light airplane, but pretty solid. More solid than a C-150 / C-152, if that's what you could compare it to.
6. Still flying mine.
7. Didn't build the kit, either time. "From plans" - not that I'll build another, but I think it's good that Sonex keeps the "plans build" option available for those with more time than money (or who just want to try it - it's not hard). One option I would consider is the pre-built spar. By far, the most time-consuming page in all of the plans is the page with the main wing spar. Paying for pre-built there is some money pretty well spent to accelerate your project. The other pre-fab stuff they offer? Not as great of a value as far as time saved per dollar spent, but I hear it's well done.
8. My home field is at 2100 MSL, with density altitudes regularly above 4000. With the big engine, it gets up and goes. But it's noticeably less enthusiastic with 2 people on board. For hot/high, I'd say the big engine is the way to go. But I would say that about ANY plane.
9. Forward visibility - as a taildragger on the ground, it's about as good as it gets because the glare-shield / panel slopes down on the sides allowing almost straight forward visibility. The wrapped polycarbonate windshield is a bit wavy to look through, so in flight forward vis - you can lose the plane on downwind ahead of you, but you get used to it. Most of the visibility is out the bubble over your head, and if you're cranking and banking as the plane was intended, most of your looking is through the bubble, which is just fine.
10. Not much snow around here, but yes, I'll run it below freezing. 3300 with the Aerocarb starts right up, no problems. I do not have any sort of heating system - just run long underwear, and the big bubble overhead provides a surprising amount of solar heating, even when it's pretty cold.
11. I have visited two Kitfox builders. One seemed to have struggled through a very long build. One problem he said he had was motivation - most of the time you're working on a collection of tubes that he felt never looked "finished". Then, nearing the end, it gets covered and suddenly looks much more like an airplane. He thought with riveted metal, it might be more motivating because when you rivet up a Sonex rudder or tail or whatever and hang it on the wall, it's ready to bolt on and fly. The other builder I visited might be having the same sort of issue. I don't know - he's owned the project a mighty long time without a whole lot of working on it happening. Sonex does seem to be beating some of the "conventions" I've heard about homebuilts - that 80% of them never get done, and those that do get done are on their fourth owner when they fly. Sonex has about 30% completion ALREADY - and it seems a large majority of the rest of them are actively being worked, and they are OFTEN completed by the builder who starts them.