Joe, you are talking to this... w/out heaps of techno jargon, this is what you are seeing manifest itself. As reputed, this is another of the Win8, under-the-covers, attributes that positively affect performance. (Now) In Windows8 memory handing is & was designed, by intent, to work as & when needed. It works 'on demand' & staying 'active' or actively 'available', in use or still needed/wanted. I know, not deny, I am not explaining this well yet, I trust you get the gist.
And, yes, if, one watches the gauges, for roughly conducting the same activities, 8 will be using less RAM than, 7.
As an aside, this is what I try to convey... that it's a worry that so much that this OS is that's valuable & virtuous & peculiar to it, ('cuse the run-on sentence) may get missed; spotlight & focus being on Start & navigating... technically it's a brilliant piece of work!