Why don't you use the freely downloadable test version of Windows 8
and try it for yourself.
http://windows.microsoft.com/en-US/windows-8/download
Product Key: TK8TP-9JN6P-7X7WW-RFFTV-B7QPF
(Good until some time in January next year...)
Note - try to use a separate disk while testing, and disconnect your
other disks. This is a safety precaution, to prevent one OS operation
(like System Restore), from possibly affecting any other OSes present.
If you don't want to waste a DVD on that, the download can also
be transferred to a USB key, using a tool from microsoftstore.
Windows 8 actually changes how it uses RAM. I ran an early version
(Developer Preview) of Windows 8, in a VM, in as little as 128MB of
RAM. The OS can be stuffed into a smaller container than some of
the previous OSes.
You may find the RAM isn't quite as filled. I actually
haven't done any testing in that regard, on the latest
version, to see if it is still improved (as bloat can
happen at any time when an OS is being designed).
You can test both the 32 bit and the 64 bit versions if
you want, and see how they behave.
The 64 bit version needs a 64 bit capable processor. That
is likely a relatively modern "P4 or better" processor. Another
dependency noticed on the last release of Windows 8 preview,
is the inclusion of "NX" No Execute in the BIOS. A few people
were denied an installation because of that (not supported
in their hardware). Which is why, running a test copy now, is a
good idea. For example, I learned only a couple days ago, my second
best computer here (Core2 2.6GHz) has no video driver, and Windows 8
is stuck at 1024x768 resolution. And Nvidia has no plan to fix that.
To run Windows 8 on my second-best computer, I'll need a new video
card.
Finally, for some "icing to stick on the cake", you can run this
to give yourself a menu-based OS.
http://classicshell.sourceforge.net/features.html
Paul