green hard drives?

For a long time, I've specifically bought the lowest-RPM drive I could in hopes of saving energy and running cooler.  That is what I thought of when I heard about the Western Digital Green Hard Drive at http://www.treehugger.com/files/2008/10/caviar-green-hard-drive-is-more-energy-efficient.php site.

You can't actually reduce the RPM speed on this hard drive to save energy.  But the heat and power reductions do sound nice.  It slowly ramps up at start time instead of jolting it to full speed. I've been a Seagate fan for years, but this could cause me to go back to Western Digital.