When Mitchell says they don't support a server operating system, they are referring to a true server setup where the hardware called the server is running server software like Server 2003, 2007 and I think there is 2009 now. This usually involves setting up a domain for everything to run in. Many of us interpreted the Network guide this way. As far as I know, no known major issues exist when operating in these environments, but it easy to refer to this unsupported concern when the answer to a problem is not apparent or forthcoming. A server that Mitchell refers to in the guide is just a dedicated computer running standard Windows software. The operative word is dedicated. Nothing else happening on that computer and NO workstation on it. No domain. Just peer to peer networking.
RAM is huge. I added the most RAM my server could handle and it did increase speed. Very noticable. Other items affect speed, like network cables, hubs, switches and the other work the server is doing. Gigabit connectivity might be a thought. I'm not there yet; only one of my computers have that port.
I doubt there is an issue with the server operating system, but SE is new and a completely different database style. There are some unknowns; little testing was likely done in this environment.
My knowledge of computers came from the numerous times I messed things up and had to fix it. Yikes. I took the 'crash' course.