I run Win 7pro on a toaster-grade box (dual core, 3g memory, graphic on the motherboard as the "server". We have about 8-9 other various laptops and desktops and print servers and such networked by LAN and WiFi. Spaghetti-grade networking by "IT pro" yours truly
The RxWriter works acceptably fast most of the time. No other issues, except that AC just mysteriously crashes from time to time.
It is often slow when I use a tablet computer (Motion LE1700) in an exam room with WiFi, so recently I have changed to just running AC from my "server" and hooking to it with the tablet by Remote Desktop. This keeps most of the calls to the database off the network, and speeds things up.
Of course, this could only work with a solo practice, since only one person can use the terminal at the "server" at any given time.
On the other hand, the rest of the staff doesn't really experience speed issues -- so I have to think it is mostly a RxWriter problem, and mostly when it is networked.