Springs provide the primary force to open and close the valves, and to reduce the required power of the EVA. The Electromagnetic Valve Actuator (a special type of soleniod, which is a device that uses an electromagnet, so your all correct or all wrong) is relatively low power.
The technology has been around a while, pioneered by a company in El Segundo CA. Formula 1 racing looked into, but it's biggest bennefit is realized at RPM below 8K, F1 engines run about 15 to 17K RPM.
Coupled with Direct Fuel Injection, all aspects of engine performance (fuel efficiency, power, emmissions, etc.) would improve about 15 to 25 percent by most estimates.
Reliability has always been a problem, as well as power consumption (requires a 48 volt system, which many MFG are considering due recent significant increases in power demanding devices i.e. DVD, Navigation Systems)