Some fair enough points.
For me, I can count the number of times I've played in the day in the last 12 years on one hand - twice! The rest of the time, it's dark dingy rooms and clubs, or large enclosed stages. Sunlight isn't a factor for me, but my short-sightedness is. I try not to wear my glasses on stage because it looks goofy and stops the rocking out, so colour for me is a big thing - with the Helix, which I've used live for 4 years at this point (only for FX mind you) I can tell what's going on in my patches at a glance, without having to read anything.
The drunk dancers thing has never been a concern for me; my crowds don't dance!
I very rarely tweak parameters live, other than using my pre-programmed expression pedal setups. But if I do tweak anything, it'll be the amp itself, which as you point out is waist height. In those rare instances where I've wanted to do some kind of experimental pedalboard tweaking thing, I usually just bend over and grab the knobs. There's a fine line between that being musical and self indulgent though, so I try not to do it too much!
There is not a significant delay when switching between scenes on the QC. It's the same as the Helix and Axe FX. There is a bit of a delay when switching between presets. I tend to design my presets so that I can do one whole song in a single preset, so I don't see that as something to worry about.
There have been quite a few people who have come to their Kempers one day, booted it up, and got some dreaded OS warning dialog box, with no rhyme nor reason for it occurring. And then it goes away again, and they're left thinking wtf. I think this is as concerning as the lack of road-testing of the QC. But maybe the QC will completely fall apart in a live scenario, who knows. I doubt it, but we don't really know either way.
Yeah we all want similar but different flavours.
I play in the day fairly often at festivals and so do many artists ( not that I'm any kind of artist ha!). I don;t change that much on the fly either but when I do, its better high up than on the floor, hence why I prefer the rack.
I've run my KPA for nearly 7 years now and not had one OS failure, including beta's, but this only means Kemper has a head start. Arguably every new release carries this risk and nothign to suggest the QC is anything but stable.
None of these are real showstoppers, just preferences. The biggest thing for me is built in amp, but that's the same for the Stage hence why the powered rack is for me.
honestly? Not making me sell the big K yet ...