All *nix systems that do a significant amount of graphics will instantly benefit from dual core eg Linux desktops. A cursory glance at top will show the X11 server consumes a significant amount of CPU time. The X protocol is asynchronous. Hence any graphics application can go about it's thing while the X server is doing it's own thing rendering graphics for the application. Anybody running TWS (on WIndows, Linux Mac) with a lot of high volume symbols on a page will definately benefit if they are running a separate charting application regardless of the 'threadedness' of the charting app. There are many examples.