...Arduino vs straight GCC:
do you mean arduino hardware? or arduino IDE (software)? all the previous posts... i read "arduino" as "arduino hardware". that maybe i misunderstood.
Sorry for the delayed response, I've been away drinking red wine for a few days
I am refering to the Arduino development environment (aka software). The only real hardware restriction is using supported parts. Otherwise you can develop on a specific arduino board if you wish, or just load the bootloader onto a bare uC and place that in a circuit of your design. So no real difference to using any other type of device.
I think most of the other posts are largely referring to the arduino software environment, because hardware wise there isn't really any significant difference to any other AVR development board (other than the widely adopted stacking thing.)