I've started to build myself a Levinson (40% ortholinear split keyboard) and I'm really enjoying the whole process. Except soldering burns maybe.
Soldering diodes and resistors on the Levinson PCBs was the easy part. I think I've finally understood how to use a soldering iron (and I also think the one I use is crap).
Building a 40% split keyboard, part 3: among various other components, I had to solder that awfully tiny thing called a metal-oxide-semiconductor field-effect transistor (MOSFET) and it was a long and painful process. Twice, of course.
That special moment when you've finally soldered everything on your keyboard and suddenly notice you've forgotten the one resistor that would require to de-solder all 24 switches to be installed properly and light up that single missing LED: priceless.
Adventures in mechanical keyboards land update: switches (Hako violet, lovely smooth, light and tactile) have been installed. Entering the hazardous "let's flash the micro controllers and solder them if they work" phase.
Keyboard micro controllers flashed, tested and soldered. It's alive! In fact I had no idea if everything worked or not until I soldered both controllers, especially with this strange mirrored master/slave system, but apparently it does.
More keyboard building adventures: everything is now set up and working. All I need is to add keycaps, then customize the hell out of my layout, because as a French user, I need access to a bunch of annoyingly accented characters.

@lectronice For my Preonic I almost didn't change a thing; and it works great

Be advised, all keyboards are ISO QWERTY, it's your OS that maps that to AZERTY or whatever. So if you assign a key to "Q" in the hardware map, that'll type an "A" on French computers

@gaeel I'm using the QWERTY international layout for my WhiteFox and it took me a while to get used to it but it works great. For the Levinson, I think I'll go for a totally non-standard, custom layout. I'm currently experimenting with various macros to set up accented characters where I like on custom layers and it's pretty cool :)