In OSX, the layering nature of windows to make drag-n-drop more usable sometimes becomes counter-productive.

There are times when I find I just want to focus on a single item and block everything else out, which forces me to either maximize Safari, or close down all my applications.

I don't care for Spaces too much right now, it's kind of buggy with Photoshop/Illustrator.

If you haven't already, you might want to give Think a try. It runs on OS X and might be exactly what you're looking for.

http://freeverse.com/apps/app/?id=7013

I'm a fan of the multi-monitor model. Two 20" LCDs are often cheaper than one 40" (not the same area, I know) and can be much more useful. My typical setups are:

screen one: rotated vertical with code

screen two: horizontal with command line and the app splitting horizontal real estate.

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screen one: full-sized game

screen two: web browser and IM client