I'm more interested in the Leonardo with the 32u4 chip myself. Much smaller than the Arduino, simpler circuit, built-in USB for higher data transfer bandwidth and comes with lots of A/D's. The 32u4 has been _the_ chip for low-cost projects that involve communication with a computer for some time now (Adafruit and PJRC [Teensy] make one), but Arduino is going to bring it to a bigger audience. The Teensy already worked with Arduino libraries, but the boot loader wasn't free and it wasn't 'officially supported'.