What are you going to do with the Arduino Uno?
Re: Arduino Uno

I'm a huge fan of the USB-AVRs. Last year I built an AT90USB162 board. Since then, I've been working on a single chip Bus Pirate clone on one and using them to build USB connected test jigs for our production line.

I also love Arduino.

I had hoped that the Arduino Uno would combine the two chips. But, I'm disappointed. My advice - wait for v1.1 (Uno punto uno?) (see @reemrevnivek below).

Looking at the Uno schematic, they haven't connected up most of the pins from the ATmegaU8 (not even out to pads). So, lots of interesting LUFA stuff won't work without big changes (JTAG, AVR programming, SD cards as mass storage, etc)

There are two lines connecting the ATmegaU8 to the ATmega328 - meant for a serial link.

My advice, buy a Teensy. If the Arduino users start coding for ATmegaU8 it'll run better on Teensy's ATmegaU4 and have acres of flash and RAM left. With the DFU/HID bootloader in the ATmega8, things must be very tight indeed.

PS. ATmegaU8 as FTDI replacement for Arduino - see Benito and Uno response.

PPS. Here's the FAQ. The U8 is a cost down.