Software development. I used to use workspaces (web on one, huge terminal + tabs on another, irc on another) but I just don't anymore. Alt+Tab between mostly full-screen windows is basically the same thing I was using workspaces for. And because I use tabs in my terminal, I don't need 30 terminal windows tiled on my desktop, plus my laptop screen is 1280x800 so it's pretty hard to have more than 4 tiles at any time if I did use tiles. The overview works well to find something visually. Instead of moving the mouse to a panel to click firefox/evolution/terminal/etc I now just Win + name the program and boom it's there. I find myself doing this all the time on older distros (RHEL) and even Windows sometimes and then wondering WTF the program didn't start.
Granted, I'm not doing much that requires me to view two windows at the same time and transcribe data between them, which is usually what people who use focus-follows-mouse and tiled windows tell me they do. Now that GNOME 3 is more keyboard friendly people will just find something else to complain about.
People. Will. Always. Complain. No matter what you do. That's just life.