I don't know about the rest of the users here but for me and other folks who spend hours if not days in front of the computer like web designers or programmers, MercuryMover is a godsend.
MM fills the need of 'old school' folks like me who are flirting with RSI, and don't need our hands on trackpads and mice, who want to keep our hands on the keyboard. Anyone who uses vi or emacs and wants their tools like that knows what I'm talking about.
Example. I have a MM shortcut [made via cmd-d] '9'.. what this does is put any window from any app to my page 2 monitor and max it to 1024 x 1280. In English: when I want to read anything in Preview, WebKit, Camino or Mail on the other monitor fullscreen, I can either go thru the laborous RSI laden mouse moving, or I can invoke 2 keyboard shortcuts and done with ANY app, not just the ones that have a fullscreen zoom.
I think it's well worth the money I spent. I definitely miss it when I move to a guest mac or one where it's not installed.