Very cool idea, although rather expensive. The Piper wallet does the same thing (off line bitcoin wallet) and it includes a built in printer, nice decked out software, for about the same price.
https://piperwallet.comI love piper but it costs more than Cold Pi and also provides less features. Cold Pi has Armory that allows you to manage multiple wallets/addresses, print paper wallets and many more features.
Actually, all you need to do is add Armory to the Piper and you have that too. Remember Piper is also a Raspberry PI but with an included printer. So technically it's Cold Pi plus printer. In reality though with both projects you're just paying for the box. The software is all open source. :-)
Yes you're right, problem is that compiling the Armory for the RPi is a nightmare..