I've have a linux install on my hdd I use occasionaly and I've been using it for the past few days.
Do you know what the first thing I noticed when i came back to Windows was?
Disk activity - Linux, I'm not doing something - it sits there doing nothing. Windows - Disk access (not constant thrashing, but probably a couple of times a minute).
(note, not and entirely fair comparison as my windows install is used far more than my linux and has a large detritus of software installed on it (inc. the stuff I have in the sys tray).
The other thing I notice: not having wobbly Windows... makes Windows feel so old
(except my graphics drivers aren't properly supported by the latest version of the kernel so no compiz for me )
Vista and 7 aggressively fill a memory cache with hard drive pages during non-peak hard drive access in order to reduce hard drive access during peak access. The effect is more hard drive access overall but faster reads and writes.