Ever since I 
hacked a Teensy into 
Cooler Master's key tester I thought this could be done more "professional" w/ a custom made PCB. Unfortunately, I have a hard time wrapping my head around PCB design software, despite the fact that I work w/ PCB's pretty much every day -- I can read schematics, trace diagrams, know electronic components -- CAD software freaks me out :/ So I bounced the idea of a few people I know doing PCB design work almost every day, last one was bpiphany (designer of the 
Costar Replacement Controllers, one of my all time favorite DIY projects) -- he came up w/ a PCB design w/in half a day and set me up w/ pcbwing to have four protos made 

 Here's the short (picture) story of how this worked out for your entertainment.
Unpacking and inspecting for fit, looking good:
 
  
 
Resistors go in 1st:

The Teensy needs to be almost flush, a piece of sticky note on the back will create a wee bit of clearance:

Teensy is set, about to start w/ the 1st switch:

Switches are in, LED's come next:

All done, switches are MX White w/ Clear springs (my personal favorite):
 
 
Fitting the assembly into the lower shell:

Cutting the hole for the USB connector is a ***** :/
 
  
Final shot:

Everything is working as planned, I'm happy 

 It's a bit of a novelty tho, I don't think there are many uses -- media controller, Dota keyboard, cursor block next to a 60% board (my personal favorite.) Not the most cost efficient way to do it either, 4 boards run at $50 (although this would substantially come down w/ volume), a Teensy is $16. Thoughts ?
Edit: Source code and hex file can be found 
here.