One of the main advantages of having plenty of memory is when working with graphics or video editing.It will save your system from constantly writing to, reading from the hard drive.
In normal use it will mean that you can keep several programs open and minimised to the taskbar, ready for instant use, rather than closing and opening them again. I have 1gb of mem. and generally on opening a program in a morning, I keep it open if I'm going to be using it again through the day.
So I at times have a couple of word programs open plus Publisher, maybe excel, and two websites open, this one and either BBCi or my local area website for up to-date info. Not necessary I know, but useful j.