I'm really, really interested in Raspberry Pi. I'm currently developing a Scheme / Lisp based OS for distributed processing (I've currently got a toy implementation, modulo a load of glaring omissions and with no "user interface" other than REPL over serial port, running on an STM32 chip); something like Raspberry Pi could be a very interesting target. With video output and a keyboard added, it could behave a lot like the computers of yore, only with a proper programming language. An almost totally "bare metal" OS which you can, and indeed have to, build stuff on top of. Much like the BASIC prompt of the '80s. Only not BASIC. So, anyway, you can count on at least a couple of sales to me.
I haven't looked into things very hard yet, but is the interface to the GPU side of things well documented and available for usage "sans linux"?