I haven't experienced any problem with the issue that you've mentioned with my Quickfire Stealth. Do you have any sources of information about the key not registering and/or a key activating multiple times when actuated once? I connect my Quickfire Stealth to my PC into the PS/2 connector on my motherboard through the USB-to-PS/2 adapter if that means anything.
User reviews. The same on the Choco Mini, actually.
Kul ES-87 seems like a good choice overall. Or the Leopold 750r. Although the Leo is a bit more expensive and harder to find in the US.
Coincidentally I found this board on my own through surfing and totally agree. It fits all of my criteria and the build quality seems impeccable. I just wish it didn't use a lower speed Holtech controller over USB. I also found the Max Blackbird. While it's not quite as beautiful and low profile, it does have a high speed controller and I can leave the lighting off. It is not cheap at all though and I know I'm paying for things I won't use, like the USB hub, lighting, and ridiculous amount of other features.
I've read hundreds of posts on Leopolds and the issues people have had with non letter keys feeling mushy make me feel very uncomfortable. It seems like if you get a Leopold without QC issues it's nicer than a Ducky, but if not, then you just wasted a lot of money.
I'm hesitant to buy a Filco. I won't bottom out my keys so the stabilizer difference doesn't matter to me. I don't want to deal with the super limited availability either.