Having had a VGT on my Series for some time now, I'll pipe up. My vanes are controlled by a cable and springs hooked to the go pedal. Vanes are forced normally open by a spring. The cable hooks to a stronger spring, and when you step on the accel pedal, it overcomes the weaker spring, closing the vanes. A boost actuator will overcome both springs when the desired boost is reached, opening the vanes. There are various configurations based on this general idea that are now running on VW engines on vwdiesel.net, and no one, myself included has anything bad to say about how they work. Also having the vanes controlled by throttle position helps with fuel economy as the exhaust is only restricted when you need more power.
Turbocharger, in your thread, you mention adjusting something that Mitsubishi put in a hard to get at place. I hope it isn't the screw that limits how far the vanes close as that is a critical factory setting and should never be changed.
Also here is a good pic showing how they work.