Vehicles designed to minimize impact on the environment should not be held to same performance standards as vehicles that use the old fossil fuel combustion engine with which we are most familiar. Given a different set of criteria, these vehicles perform well and are step in the right direction. New vehicular technologies should be accessed according to their impact on global emissions. Natural gas vehicles are a step in the right direction.
No, natural gas vehicles do not perform well, because they are inherently inefficient. If they performed well, they would be popular already. Because they are not popular, they must be flawed. Consumers are smart, and they want the best-performing products. Because natural gas vehicles have not caught on, they are not high-performing vehicles.