Arduino around the Xmega? I came across a dev board around the Atmel Xmega controller. This an AVR like used on Arduino, but with a lot of extras. 



I was surprised to see that the board is hardly more expensive than an Arduino, despite:


  
  384kB of Flash (versus 32kB for Arduino)  
  DMA  
  Xmega can run at 32 MHz (16 MHz for Arduino)
  on-board OLED display  
  on-board light and temperature sensors  
  on-board microSD socket
  


For all these on-board features you'd need a shield or breakout board for Arduino. I seems to me that for a lower price than Arduino you could build a much more powerful system, which is Arduino-compatible.
How hard would it be to port Arduino to the Xmega?

see also http://www.element14.com/community/docs/DOC-71436
There's an attempt to get the Atmel XMEGA boards working in Arduino IDE.

https://github.com/akafugu/Xmegaduino

It's not fully featured yet but appears to have to features to allow you to start hacking with this board.