I started using a OLKB Planck a few months ago; it's been odd but very interesting--the customizability is darn near absolute, so you tend to figure out quickly what keys you use the most and where is most convenient to put them. Definitely not for everyone, but if you're adventurous and picky about layouts, they're worth trying. The worst bit is trying to find good ortho keycap sets at a reasonable price...
Yeah I built a Corne split keyboard a few years ago but I'm not a fan of tiny shift keys. I hear those ortho/planck layouts are great for the more efficient letter layouts like colemak or dvorak where you aren't reaching all over the place as much.