I have yet to see a single argument for Dashboard (minus the guy with the security camera widget) that can't be as or more easily done with a combination of Spotlight (calculations, conversions, currency), Notification Centre (world clock, calculator, calendar, weather) and putting iStats in the menu bar.
As long as Spotlight doesn't have a dedicated gesture, it's not as good. Now I need to move the pointer to that tiny icon and click it. Dashboard is a simple four-finger swipe left.