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I would hope the potential benefits would be obvious to anyone with a grounding in how internal combustion engines work.
That said, solenoid-operated valves have been "just around the corner" for at least two decades so far. I'm not holding my breath for them to show up this decade, either.
As far as I know, the BMW Valvetronic system used a combination of changing the cam's rotation, and changing the lifter or the pivot point of the valvetrain's rocker arms to control the timing and lift of the valves. The information is pretty foggy in my head, though. The rotation part was actuated by oil pressure in a passage that twisted the cam pulley relative to the cam itself. I don't remember how the other was actuated.
From the videos I have seen, the Fiat Multi-Air system also uses oil pressure to work. In this case, the pressure is provided by the motion of a cam follower pressing on a reservoir. The pressure in the reservoir can apparently be bled off or directed by solenoids. It is one step closer, but is not a solenoid-operated valve. It sill has the camshaft and some fairly conventional valvetrain components. But the benefit of being able to (more or less) select from an immense variety of cam profiles for those intake valves is pretty darned sweet.
-soD
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