I have been holding XBY for a few months now, I got real excited about it when I read the whitepaper. The thing can be HUGE if they are able to accomplish what they set out to do.
The risk with XBY is their anonymous team, and that their actual code is currently not open source due to a pending patent. The patent is supposed to be finished in the next month or so, then that will let them open source their code and begin testing their actual system.
It's definitely a high risk high reward type of investment, but imo everyone needs some risk in their portfolios.