OpenXC effectively just moves "proprietary vehicle knowledge" into firmware from client software - it's not a standard interface for cars, but rather a standard interface for car interfaces.

That's a neat idea since it prevents every app from needing to handle CANbus and whatever other proprietary signaling each vehicle uses, but it doesn't really expand vehicle support because the CAN and other messages still need to be documented officially (as Ford have done) or reverse-engineered.

The current implementation of OpenXC actually makes the setup more expensive, as well - an OpenXC module, since it does more, requires more hardware than a simple CAN-to-UART/Bluetooth gateway like an ELM327 clone.