Ok, I never compared Vista to OS X, I compared Vista to XP. So go ahead and try to change the argument. For the record though, I do not see Leopard eating up RAM and CPU cycles while sitting idle the way I do see it happen in Vista.
The issue with hard drives spinning needlessly is is common issue with Vista and it is usually related to its SuperFetch feature which a lot of people are disabling because they don't want it shortening the lifespan of their drives.
Having free and unused resources is most certainly not stupid if you are not even using the computer for anything, or only for small, minor tasks. That is the exact opposite of efficient, and correct me if i'm wrong but this was an argument about whether or not Vista made efficient use of its resources.
As pointed out to you, Modern operating systems (Windows Vista, Mac OS X and Linux) USE memory instead of leaving it empty.
Efficient does not mean empty.
Having three empty seats and an empty trunk is not efficient use of the space in your car.
Having those seats filled and a suitcase in the trunk is a much better way to use that space.
When you need to use the RAM, Windows Vista (or Mac OS X or Linux) may already have cached some data in RAM (= faster loading) or it will simply drop some cached data from the RAM and load your data from the HDD like normal - totally transparent.
What you are suggesting is that somehow Windows Vista runs wasteram.exe that fills 4GB of RAM doing nothing. Logically, if that did happen, then there would be no RAM available to launch programs - that is obviously not true. Think about it. If Windows Vista was "using" that RAM for bloat/wasteful purposes it would be unable to free it when needed by a program.