Right now about 515 MB with CPU usage hover around 17%.
There's something about Vista where it uses all your memory or something so that programs run faster. 
Better than mine, mine uses 660 MB without ANYTHING I start running, CPU kinda jumps around, and when I open WMP the memory usage jumps up another 200 MB.
Get more RAM and a better CPU? lol
And yes, Microsoft took that notion from Mac OS X. Keeping RAM pre-wired so to speak makes things run faster and smoother.
Oh and here is my desktop:
