I have a Quad Core Intel PC with 4GB of RAM - I've been using it over a year to run web server stress tests (ab.exe -n 5000 -c 500), encode HD video, play games, open dozens of tabs in multiple browsers (simultaneously), worked on multi-layered +8000px art in photoshop and just about every other thing you can think of.
As of yet I've never passed 2.3GB of RAM usage. How in the world do you use all 4GB? Is there any use for it?
Update I started-up Photoshop with a 8000px (+350MB) PSD and another (+30MB) 5000px PSD. I already had Chrome running with almost a dozen tabs open. Then I started Firefox (with all my addon's) and opened another 10 or so tabs. Apache 2.2 is running to serve PHP files. Last I have a 700 song playlist playing in windows media player. I guess I could have started open office too - but I never use it. Here is what task manager shows:
I guess I could just keep opening programs until I don't have any taskbar space left - but that would be an unrealistic example. I never run more than 5-7 apps at a time for my own sanity.