I go with the (distribution) flow and use KDE/kwin. I dumped Gnome/metacity a while ago as it wouldn't do more than 12 desktops, while kwin gives me 20. F1-F12 for the first 12, Alt+F1-F8 for the rest. Every major window is fullscreen on its own desktop and can thus be switched with one keypress (I like desktops over some sort of window-focus hotkey as it gives me a spatial metaphor to how keys are assigned). For example, I'll bounce between web (F7) or pdf (F6) while editing code (F1/F2), negating the need to have two windows side-by-side with the management/tradeoffs that incurs.