The rapid growth of on-demand ride services such as uberX and Lyft, or “ridesourcing,” has prompted debate among policy makers and stakeholders. At present, ridesourcing’s usage and impacts are not well understood. Key questions include: how ridesourcing and traditional taxis compare with respect to trip types, customers, and locations served; whether ridesourcing complements or competes with public transit; and potential impacts on vehicle kilometers traveled. We address these questions using an intercept survey. In spring 2014, 380 complete surveys were collected from three ridesourcing “hot spots” in San Francisco. Survey results are compared with matched-pair taxi trip data and results of a previous taxi user survey. We also compared travel times for ridesourcing and taxis with those for public transit. The findings indicate ridesourcing serves a previously unmet demand for convenient, point-to-point urban travel. Although taxis and ridesourcing share similarities, the findings show differences in users and the user experience. Ridesourcing wait times are markedly shorter and more consistent than those of taxis, while ridesourcing users tend to be younger, own fewer vehicles and more frequently travel with companions. Ridesourcing, like taxis, appears to both substitute for and complement public transit; the majority of ridesourcing trips would have taken substantially longer if made by public transit. Impacts on overall vehicle travel are unclear. Future research should build on this exploratory study to further understand impacts of ridesourcing on labor, social equity, the environment, and public policy.