Using Whistler Pro Beta 1, and i just upgraded to 256MB all of 2days 13hours 28minutes and 34seconds ago (hmmm, gotta love the reliability and uptime of it

). All i can say is that it just ROCKS. There is a very noticable difference, because it almost never swaps now whereas beforehand it was crunching the hard drive to death whenever I got into some relatively normal multitasking. Games show quite a difference too, in both load time and initial frame rates.
Go get yourself some ram, NOW !
EDIT: Typos, and " 2days 13hours 32minutes and 19 seconds "
hehehe.