If you type PS2 HELP you will get a list of English commands that should be self evident. The major command settings take effect forever. The obvious useful ones are the Power timeout (machine switches off after X time), the LCD power timeout (Display/backlight goes off after X time) and the keyclick.
Most of the others have keyboard equivalents - notably FN-F11 switches the CPU speed under battery power between low medium and high. This can be very useful. I generally run at low speed except when compiling software on the machine.
Ultrachg.com is a small program that toggles charging of the battery while the machine is running. This seems to work fine with the 240v 30Amp PSU I have at home but the 1Amp PSU I run at work doesn't like combination charge and run. Run the program once as "ultrachg enable" and from the next battery charge it will charge while the machine is running. The setting takes effect happily under Linux.