I just finished my x0x...got it all tuned and it sounds amazing. Nice, classic 303 sound, I love it.
...you know what I loved even more?
I ran the VC and gate outputs into my Doepfer modular, and it's pure evil. It's like having a 303 on crack...no make that heroin. I can get 303 style sequences going, then run it through multiple oscillators, a suboscillator, and then my choice of filters, like my Harvestman Polivoks filter...then a VCA controlled by a full ADSR envelope module. This goes way beyond the basic sounds of a 303, but it's really nice to have that functionality to get some extra variety out of this thing. Thanks to the designers of this thing for adding the CV/gate functionality to it. Only 1% of the x0x users will probably ever use it, but for those who do, it's wonderful.
If you have a modular, or maybe something like a Moog, you have to try the VC/Gate outputs on this thing!