Okay. I'm old school.. I started with UNIX System III back in the day, so I've worked on pretty much every UNIX there ever has been, including all the derivatives and clones... Xenix, SCO UNIX, SVR4, BSD 4.0, 4.1, 4.2, SunOS 4.x, Solaris 2.x, HP-UX, Apollo Domain/OS, Linux kernel 0.99 days, ... Now that I think about it, I've never written a single Windows program !
I'm an EE and spent half of my career developing hardware for these various platforms that run these various OSes and writing device drivers for them.. and half of my career at software houses writing applications (SunView, OpenWindows, Motif, CDE, X, GTK, etc)
I've had my Pi since the first batch was released for sale last year, and so I have a Rev 1. board. I was interested in it mostly as a low power media server, but I've since been experimenting with the GPIO ports and turning it into a small key-server for my network with a keypad for single-factor authentication (i.e. a PIN pad) that's still a work in progress, but its fun to do anyways.
On the authentication side, I am interested in the camera module to enable key-serving with facial recognition as a 2nd authentication method. This then becomes a 2-factor authenticator. So I have a little project ahead of me here.