First rule of keyboard real estate: Layout, layout, layout! For me, the HHKB layout is perfect. I also like the form factor, Topre switches, keycaps, and overall design/aesthetics of the board. I keep others in my rotation (including a custom 60% with brown Alps, V60MTS-C, IBM XT, RF87UB45, and RF87UB55), but I keep coming back to my (silenced and lubed) HHKB Pro 2.