I believe it is completely impractical as an automotive fuel.  Its physical properties make it too expensive to transport and store and its combustion properties make it a poor internal combustion engine (ICE) fuel.  It works well in fuel cells but these are much better suited to stationary power applications than automotive applications.

For more information about hydrogen and its use, the US Department of Energy has published the College of the Desert's Hydrogen Technician's Manual:

• Hydrogen Properties
• Hydrogen Use
• Hydrogen Use in Internal Combustion Engines
• Fuel Cell Technology
• Fuel Cell Systems
• Fuel Cell Engine Safety
• Fuel Cell Bus Maintenance
• Fuel Cell Hybrid Electric Vehicles
• Acts, Codes, Regulations, and Guidelines
• Maintenance and Fueling Facility Guidelines
• Glossary and Conversions