We are aiming for about 100 users per CPU
Must be a typo. Otherwise, this is going to be the most expensive MMOG system ever developed
. (EDIT: in setup and admin costs - mulitplying your hardware by 10-20 to get the extra CPU's adds a heck of a lot to costs: much bigger setup cost, much bigger maintenance cost)
FYI I've seen 20k+ player MMOG's running in pure java wihtout middleware with > 2000 players per CPU on 1Ghz intel processors.
So, even 1000 players per CPU isn't impressive, unless Doug was talking about 400Mhz P-2's
With expert middleware running your system - e.g. GrexEngine, Zona, or any of the other java MMOG systems - I don't see why you'd expect significantly fewer than 3000 players per CPU for a typical MMOG. (although, of course, I could easily write you an MMOG that could barely handle 50 if I were being perverse