code for Linux and code for AVR are two totally different beasts. With AVR, I feel that you could just drum up a quick hack and have code running within a couple of hours. With Linux, I always felt that you need at least a couple of days to get things to going (eg, having a root fs structured, choose a kernel, make sure that your memory map is set up correctly etc). Maybe, I have been away from embedded Linux for too long and the goal post have shifted towards a better location.