I read jcs's article about hacking the MailStation a month ago, and decided to get started hacking the Z80. I adapted his original USB-parallel "tribble"-based Teensy sketch for an Arduino Nano clone, and was able to send programs from my modern-ish laptop to the MailStation. I had started planning the design of a bare-bones AVR-based PCB in my head, but hadn't yet started to put CAD to disk. As soon as I saw the announcement for the WiFiStation, I ordered one.
Assembly was easy - no precarious situations with the soldering iron, and it came with all the headers and sockets needed to make the board extra-maintainable.
The open-source ISC-licensed repository made it easy to load a program over USB. I haven't yet tested the wireless functionality, but that's up soon, as well as installing a LiPo battery.
The 3D-printed case snaps together nicely, and the black color almost blends in with the original MailStation's case.