Hi,
As a concrete example of hdparm, here are my settings:
/sbin/hdparm -X66 -d1 -u1 -m16 -c3 /dev/hda
You will need to run this every time you boot the computer.
I understand these are very standard settings for even vaguely modern hardware, so they should be safe although as always, it's your liability. I think you know you can test your drive's read performance using hdparm -t, so try this before and after.
Distros have to be safe by default, so they don't use hdparm. I don't really see why there isn't a deb for it though (with debconf to set it up - I think hdparm.deb just gives you binaries/docs).
Alexis