My buddy had one, and we played Super Street Fighter 2 for hours.
It's definitely not usable today although there's some folks working on a X-Band 2 for PC emulation gaming. Don't know if it's current or if it was abandoned.
Sorry man, Xband ran through a centralized server. One that shut down, the entire service went with it. It made me mad on the last day, because they killed the server that morning instead of towards the end of the day.