I use that one. That's for like...when you have, say, 5 photoshop documents open and about 25 other things. If you hit Exposé All Windows in an effort to see your photoshop documents, they'll be so darn tiny you won't be able to tell them apart, or find them, because the other 25 things will be tiled among them. With Application Windows, it just tiles the active application's windows, which would only make those 5 photoshop documents tile above the other 25 or whatever windows. Then, you could concentrate on just choosing between those.