If you don't know what it is, it's two Sega Genesis (Mega Drive) sound chips (Yamaha 2612 in V1, and uhh, some other number in V2) in a small aluminium box with a boatload of faders to control every aspect of each operator, some LFOs to modulate them, and an arpeggiator/sequencer (I never use).
You might think it sounds like a Sega Genesis game all the time, but it does not. The LFOs really open up the 2612. It does some amazing performance tricks you certainly don't hear in Sonic the Hedgehog. But, it does those, too. Channel your inner Yuzo Koshiro, then make it sound like something entirely else.
A while back, Twisted Electrons saw fit to make the firmware open source, and it's wonderful how much functionality they've added. Looping envelopes that can loop from different points in the six-stage envelopes, new voicing options, a MIDI tool to change settings from your PC, heck, a couple weeks ago they added the ability to change the scaling of the envelopes. It came out four years ago, and the updates keep on coming.
Just so I don't sound too much like a fanboy, I will qualify that it is a bit of a janky box. Voice stealing is weird sometimes, and these chips are noisy and scummy sounding. It's probably the most analog sounding digital thing I've ever heard. I guess there are still a few minor bugs with the firmware, but none that I personally notice.
Still, it's only 450 Euros and eminently worth it.
Well, I've been messing with 3.6, and I'm not entirely sure when they fixed it, but the voice stealing that I had trouble with before (hold a note, and the sixth/twelfth note you play along with it depending on the voicing mode you have chosen steals the held note) appears to be gone. You can hold notes indefinitely while playing other notes, and as long as you don't play more notes than your chosen voicing option, the held note stays. That might have been my biggest issue with it, and it's gone. Hnnngggh! SO good.
I opened mine up and resoldered a bad LED. Funny how doing that makes you more attached to a piece of hardware.