From my work experience (TCS/VDC), and from what I read here and elsewhere, I think it's worthwhile posting this. There are some misunderstandings on when and how to use the VDC OFF switch.
First of all, the actual VDC portion (cornering control) should only be turned off for fun in the corner AND ONLY IF YOU CAN HANDLE THE FUN OR ACCEPT THE CONSEQUENCE. The proper usage of the switch as described in the owner's manual only pertains to the TCS portion (drive wheels' drive slip control). Nevertheless, both VDC and TCS are turned off together with that one switch.
As many people here found out, it's hard to do better than the VDC to have fun at the limit. So I would simply recommend leaving it on for normal driving. But there are times when normal drivers can do a better job with the TCS off. However the way to do better, as described in the manual is pretty much wrong.
Most people's idea of doing better than TCS involves having more wheel spin than what TCS allows. Well, it is just as important to know that there are only a few surfaces for which a car can benefit from more wheel spin. All those surfaces share one thing in common -- thick layer of loose material: thick gravel, thick snow, thick sand, loose mud. Your acceleration will suffer from wheel spin on ALL OTHER SURFACES REGARLESS OF CONDITIONS.
For example, if you are going up an icy hill, and feel like TCS has taken away too much engine power causing you not to be able to climb, you will NOT be able to climb even if you turn off the TCS and floor the throttle. Reason? While taking away engine power sounds bad, power is only good when the surface can handle it. On surfaces other than the above mentioned, the traction actually decreases as the wheel spin increases beyond the limit set by the TCS. That means even though you can make the engine output more power, less of it actually goes to the road to push you (more gets lost in your drive train).
So for those who have "experienced" better acceleration on ice with more wheel spin, it's not the wheel spin that helped. Maybe you went back and gave the vehicle a little more momentum going up the hill. For those who found TCS cutting too much engine torque at the launch on dry and wet asphalt, that feeling is right. But it's not because dumping the clutch and cooking the tires is the best. It's only because of the bad performance of this particular TCS system. It wasn't able to control the wheel spin at the launch to its target, which would have beaten the drop clutch burn out launch (many of you know that too).
So if you are convinced that you should only use the switch on those loose surfaces, here is how I think you can best use it. And most likely the G only needs to worry about snow.
Your number one target is to not get stuck at all. Say you are moving, coming up to some deep slushy snow. If you think that you might not be able to drive through it with TCS on, turn it off BEFORE you get in it and step on the throttle. After you get into the snow, keep pushing with some wheel spin. You will kind of paddle through it. Don't need to mash it and hit the red line, and do realize that wheel spin causes loss of stability (so be careful if you are turning at the same time).
If you do get stuck and stopped in deep snow (parking lot for example). Don't blindly spin the wheels. If you tried some wheel spin and the car isn't even moving, stop. More wheel spin will only dig a deeper whole and make it more difficult to come out. At that point, only rocking can help. Or just ask people to push you. Once you get moving, then you can use some wheel spin to again paddle through it, hopefully (and don't stop to thank those people. Tell them ahead of time that you'll have to keep moving
).
So that's it. If you can't remember everything, remember this. For proper use, only turn it off for deep snow that you are or might get stuck in. And use it mostly while moving to keep moving. Don't dig a whole while it's not moving. And don't use it on any other hard surfaces (ice...)no matter what you intuitively believe. And remember, there are situations that the G simply shouldn't be in in the first place, with or without TCS/VDC.
I'd be more than happy to discuss any experience you had that doesn't match my description here.