I only used the ride-sharing function of Uber when I tried it out for a week; left it on from Saikung to Tai Po then to Kwai Chung not 1 single ride sharing customer, now I uninstalled the app =P
They limited it to 2 shares per day, not sure if this will change now. I thought they were trying to promote the actual taxi side of the business with the limit (so not all drivers will just drive around picking their own destination rather than letting passengers choose where ever they want to go)