When I originally installed Windows 7 64-bit, I had 4GB in my machine. While the performance improvements I saw were noticable and appreciated, it was clear that Windows 7 was more than happy to consume all the RAM I could possibly throw at it:
After a full day of use, Windows 7 Resource Monitor looks like this:
While the performance difference is not night and day for me, I will say that the first thing you notice is that the more RAM you give Windows 7, the less often it seems to hit the hard drive.
I have some fairly monsterous Firefox working profiles and Java IDE configurations that by all accounts brought my old Windows XP and Vista installs to their knees on loadup. Now with 8GB in Windows 7, my disk blinks lazily along while everything stays completely responsive and whatever I’m loading fires up in half the time (give or take).
What is great is that you can even do 12 GB for under $180 if you wanted to go even bigger.