Its monophonic as well as 2 note paraphonic (not quite duophonic because the envelopes and most of the signal path are shared). It has after-touch and a step sequencer too.
Its got the multidrive from the regular sub phatty plus its got the overdrive (like feeding the headphone out from the mini model D into the filter input). Filter are slopes directly accessible from the front panel. Basically everything that I thought were the shortcomings of the previous Phatty lines.
Looks sweet! Should be coming out in May of 2014.
Check it out at Moog