I've ordered an LPC1343 Cortex-M3... I'm sure that there are Cortexs with higher pin count, but hey just check that it even has an embedded USB client - host!!! (I think at least)
I know a lot of guys here like webbot have been trying hard to make the Axon series look so extremely slick but hey...
An atmega at 8bit - 16MHz, can't be even close to a 32bit - 72Mhz ARM!!!!
Problem is that NXP don't release them with a free IDE (at least not totally free.... you can work out with the Demo for some period, but that's just NOT nice)
I know Atmel has some ARMs around.... But just for compatibility's shake... Wouldn't a Atxmega128A1 come just in handy?
At 8/16bit - 32MHz it would make a deference...
Problem is that you should also teach the world how to use 3.3V instead of 5V... Some servo users wouldn't be so happy with it...