Windows is ultra-conservative when it comes to using your RAM (doesn't scale like I, and others surely wish it did) so when it comes to basic Windows features it won't use too much more RAM but it will be slightly less stingy when it comes to allocating more memory to programs.
It's also the type of thing you won't notice immediately without heavy intervention so don't let a temporary install sway you too much. With the RT7Lite version of Windows 7 x64 I put on my mom's computer it used around 700mb of RAM at boot whereas now it uses around 900mb at boot(She has 6gb total for reference, 2x1gb/1x1gb per channel). All she does is light office work and play Cityville so there is next to no difference between when it was first installed and now(besides it using more RAM now).
Oh, and most importantly - It has definitely made Waterfox and MS Office load more quickly and run more smoothly
Edited by Ryleh - 2/14/12 at 8:50pm