My Mini DisplayPort —-> DVI adapter arrived today, so I was finally able to get my PCs monitor working with my Mac. The results are quite full of win. (Click for larger versions of the pics)

With some windows open

If you are curious how Spaces handles extended desktop when you go out to the “birds-eye” view: The secondary just turns black, except for the transition animations when they appear. On the primary, you see this, which is a little awkward looking but a good representation of how the windows are actually arranged:

Lastly, setting wallpaper and display settings. Opening the Displays pref pane spawns two windows. One controls the res and color of the 2nd display, the other controls the same for first screen and has a third tab, labled “Arrangements”. Here, you can turn mirroring on and off, and drag your screens around to arrange them. The primary is whichever screen has the menu bar on it. You just drag the bar to the one you want as your main. The Dock will follow the menu bar; both only show up on the primary. This can’t be changed. Clicking a screen will ID it by flashing a red border on it. It will also show a thin red line on the side screen(s) next to it, to help you get things arranged with how they are in real life.

For the wallpaper, opening the Desktop and Screen Saver pane also gives you two Windows, each mostly identical, one on each display. That sets the background for that monitor. I say “Mostly” since the switch for the transparent menu bar is only on the primary, since it obviously doesn’t need to be on the others.