Any point to having green HDD's power down w/modern OS's?

In the power profiles for Windows XP and 7 there is an option in power settings to specify how long to wait before powering down a HDD (which I assume
means stopping the platters from spinning and retracting the heads). I remember 98SE would spin the HDD's down eventually and leave them powered down until I woke them up. But considering modern OS's always seem to have a reason for writing/reading to/from a HDD even when no human being is using the system what's the point? Or are there intermediate power down modes (maybe keep the HDD spinning but retracting the heads, or reduce the RPM of the platters)?

I wouldn't bother, no.

I do not know of any other intermediate options either, sorry.

ED is disabling power saving for the HDD a better choice in terms of increasing HDD life?

I doubt it names much of a difference. That opinion however is based on a guess.

WD Greens will go into a low power mode regardless of whether you have it set to do so on the OS. So regardless of what you set in the OS, WD Greens will still power down eventually. I do not know if this is the case for "green" drives from other manufacturers.