alot of my friends have 4gbs of ram
and it does come in use when you run alot of programs running alot of the times
also if your a gamer and you use vista then it is necessary, vista has got to be the biggest ram hog ive ever seen
and since you can get 4gb of Gskill for like 220 bucks (using there cheapest 2x1GB) i dont see it as a waste