Yea, you will notice a big difference.. windows xp alone uses.. what like 256 megs or more? Sitting here idle with IRC open, virus scan up.. himach (or whatever its called), and Firefox I am using 106 Megs of ram. I still have another 143 megs left.
So, yea, when I went from 1 to 2 gigs a year ago, I did notice it.