Well, the memory that I installed not long ago has resulted in some improvements. Web browsing in Internet Explorer and Firefox has remained the task most affected by adding more memory. It definitely helps in games when loading content; World of Warcraft loading times are significantly decreased, and Oblivion's are somewhat reduced. Photoshop gets use out of it too, though I usually don't have more than a couple hundred megs open in Photoshop.
Not a big change, but a decent enough one, I guess.