Atxmega microcontrollers are great transition between 8-bit AVRs and powerful 32-bit ARM mcu’s. Great thing with them that xmega uses pretty same AVR core which is just 16-bit instead 8 and have more powerful features included like DMA, Event system, faster ADC and DAC. Everything sounds great just one thing – programming is a bit different than we used to with 8-bit AVR. It uses PDI interface instead of ISP. And if you have a pile of ISP programmers purchasing or building another one for xmega doesn’t sound very attractive.
szu have done great work to solve this problem. He was able to adapt USBASP to support PDI protocol. He altered USBASP firmware which can be uploaded to existing usbasp programmed adapter. AVR support also remains in tact. Another thing you should take care of is to reduce voltages from 5V to 3.3V and change programing header wiring a bit. There is an AVRDude patch available so you could program using this wonderful command line tool. This is really plausible effort to make things more easier and accessible for us hobbyists.