On the Mac, I'm a bit of a SizeUp junkie - it becomes so much an intuitive part of your computing experience that its command keystrokes eventually get baked into your fingers' muscle memory. I bought a license, and after a few months of use, I couldn't even tell you what the key bindings are, my fingers just... know them.
Praise for Winsplit Revolution
As soon as I reach the office though (to sit down at a Windows XP workstation), I feel like my multi-monitor setup is messy and slow in comparison. This week's discovery of Winsplit Revolution changed all that, it's exactly what I wanted it to be - "SizeUp for Windows". Now my obsessive-neatness tendencies are catered to and I can setup beautiful grids of terminals, browsers, and editors.
I'm not really one of those compulsive tweakers and customizers who must absolutely change and configure every aspect of their graphical shell; I prefer when software just gets out of the way, lets me work and read, and doesn't obstruct my feeling of being in control of the machine. Windows itself, without keyboard shortcuts, makes you feel like you're interacting with a computer, not the apps themselves - the power of this kind of tool is that it gives you the illusion of apps reading your mind and moving to the right screen/edge/corner with a few twitches - the OS isn't standing in the way.