I have many Model M's I've bought at thrift stores in the $2 to $5 range. When one gets too much jelly and breadcrumbs in it, I set it aside and pull out another one. They're sometimes still found in the same thrift-store bin as the pile of cheap lightweight plastic PS/2-interface and "modern" USB-interface computer keyboards. I'm typing on a Model M now. I also have a couple of IBM AT keyboards, they rock but they're also very clickity-clack loud. The AT keyboards work on modern "PS/2" interfaces with an adapter for the AT's large DIN connector. Don't try to use a PC or XT keyboard on an AT or more modern machine, the connections and data format are different.
I'm not into case mods or any of that carp, but this "typewriter keys" think does look neat. What I'd really like to do is my own microcontroller in the keyboard, add a small LCD display, and make "macro" keys like a macro key program on the PC, but all embedded in the keyboard. Adding a little more ram/flash and a battery, and the keyboard could make a self-contained computer/word processor.