Having no problem here with the compatibility tookit res change fix with kegetys d3d9 dll file... Im using 1680*1050 res on a Dell 20" widescreen. Flawless so far..
If you all have alt - tab troubles and really need the access to desktop you might want to try this little tool : -
http://grismar.net/shiftwindow/
what this does is allow you to set your sh3 (or any game) ini or from ingame options to "window" mode, but at same time target the application running "SH3" and then hit the trigger button in the shiftwindow application, and your window mode style becomes full screen effect. It removes the window border edging etc then applies the whole thing to full screen.. This there in allowing one to select and use any application running on taskbar, with alt-tab, or use windows key for start menu without effecting game..
Basically it is window mode but you get same view as in full screen.. great tool and I use it in many games if messing about with loads of things at same time... specially when games wont behave with alt-tab..
Cheers,
James.