Just a comment on Chris's last point:
Also, I don't get the obsession with the Pi. There are now lots and lots of under $100 ARMv7 dual core (!) boards that run Linux and have way more I/O options. Why not get something not totally out of date to begin with?
My personal reasons for being attracted to the Pi are, 1, that it's vastly better engineered and supported than other linux+ARM solutions I've seen; and 2, although I'm not sure about this, it seems to dissipate much less power than ARMV7 soutions making it easier to make standalone gadgets with it.
cheers Miller