This is a good and useful thread to have
One thing I did notice from another forum is that it is best not to power down the PRS-600; rather just leave it on and it switches to sleep after 60 minutes.
When you next switch it on it comes to life almost instantly.
I believe it uses very little power on sleep but booting it up or shutting it down consumes rather more.
This is quite a nifty feature and one Sony use on most of their mp3 platers also.