Today I have had the pleasure of working on a 23 inch Apple Cinema display. It runs at a lovely 1920x1200 resolution - that is a lot of desktop real estate. The reason I wanted a larger monitor more than a new computer was that I was struggling to use the smaller monitor for all my work.
The sacrilege I am bestowing upon this beautiful piece of hardware is that I have to work on Windows (and more specifically the beast that is Vista). What this showed me is Windows is rubbish for working on large monitors in any meaningful way.
The problems? Simply most software designed for Windows is designed to work in full screen mode (and much of the development tools encourage this). In most instances this is complete rubbish when you are working on a large monitor. Even the two monitor configuration encourages you to still work with each screen using full screen apps.
The main problem is that the window handling and the taskbar itself just isn't up to the job of context switching. This is partially because MDI interfaces (either traditional or tabbed) are controlled by the application not the OS. The actual windows are also not broken down into functional elements. Even editing in Word encourages you to use fullscreen.
From the demo I had of Mac OSX it deals with multiple windows much better, also all the time I used Linux (KDE and Gnome) it felt like it was geared for large screen use. It is partially the reason that GIMP works much better on Linux than it does in Windows and people using Windows have immese problems with the UI.
If large screen computers somehow become the norm I think that Windows will need to come up with a more intelligent way for the user to use the space. At the moment the resolutions we have are great, but having a more sharply rendered image is of less benefit than using the extra space more efficiently.