Nah, haven't done any of them even though I have both controllers...I can't see the big problem with the A590 and the extra psu since the A590 powers up together with the A500.
On the other hand I can see the benefit on the GVP since you have to turn the psu for the hd on first, unless you want to break anything. Since my GVP psu has a defective case at this point, I will make the mod, unless someone will convince me that I'd better not :-)