It's a shame M15s are so damn rare. I'll be honest, I'm super curious about them. Don't know that I'm $500-1000 curious, but I'm definitely curious.
I hear you... As a lifelong Model M user I wish I had one but the price is a little too steep. Or I can try to be lucky like with this Cherry MX 5000 that I got for 228 Euros. Or maybe just sell this Cherry MX 5000 NIB and use the money + a little something to buy a M15.
Terrible thing is: I do like split keyboards (I even own an old rubber dome split Belkin keyboard that I used to use when my gf was asleep as to not bother her too much with the buckling springs). And that split Cherry MX is surely better than my rubber dome split Belkin but still, I fear that it's like what you're saying:
But I think you won't be able to get even close in feel to a buckling spring with any cherry switch. I've tried them all but reds, and while blues are the closest, they still just feel wrong. And weird weird weird.
Then it makes no sense to risk to ruin a NIB highly collectible keyboard just to find out anyway that I don't like the "Cherry-MX-whatever-color-from-the-rainbow-plus-whatever-spring-mod".
I may just re-list the thing. Don't know.
Anyway I'll start a new thread or PM you one of these days regarding these modifiers settings you're using under both Linux / Windows / OS X and the "super-only desktop shortcuts" that don't interfere with any program. It makes a lot of sense and I've got questions for you : ) (nice avatar btw, I love cats and that one is great, it surprises me some people don't like that avatar : )