I thought the pageouts was what you need to look at to determine ram usage. Page ins are info going into the memory where-as page outs are info that is being moved out of the ram to the vram on the hdd to make room for new info coming into the ram.
I'm no expert but that was my understanding of it.
I do know that I just took out my stock 512 and put in (2) 512s yesterday and the difference is night and day. And my page-outs have nearly disappeared.
I used to run about a 2 to 1 ratio, 2 page ins to 1 page out. For instance if I had 40,000 page ins with the 512mb ram I might have 20,000 page outs.
After installing the 1gb ram yesterday evening, I checked this morning and I had 40,000 page ins and only about 800 page outs.