Well I've only had a few people download the client and test the game server. So being the impatient person that I am I trimmed out a lot of code from a copy of the client and made a zombie test application.
It basically logs in just like a regular client, and then simulates ship movements. I have them starting in random places and random distances from the sun, and then I run them through a planet orbit subroutine. So they just circle the sun in randomly placed orbits.
At the highest point that my workstation could handle I had 22 of these test apps running with no significant degredation in performance on the server. In fact, I don't think the server was really breaking much of a sweat. This was on a 100 Megabit LAN of course..
I left it running overnight, and at some point this morning all the test clients on my workstation locked up. Probably hitting the swap file for to long of a span of time. 16 of the apps running at the same time took up almost 4 gigs of memory, and I've only got 2 installed.
Next step is to try and get around 100 test apps pounding on the server and see what happens. First I've got to get a new video card in my production server. It has a crappy Intel onboard video card and wont even run the text only server app.
Don't think, just code.