The Widget Bar
(Apple does NOT call it a dock--I just looked at their docs) doesn't LOOK like the dock, nor does it ACT like the dock. That should clear up some misconceptions
The Widget Bar acts very much like the media bar of many apps. Click an item to activate it--or drag it where you want it. That means you can add a widget with one click if you don't care where it goes. Or drag it into place if you do. It's really not confusing to use.
And the Widget Bar isn't a normal part of Dashboard use. It's for customizing what shows up in Dashboard. The rest of the time it's not even there. Many people will never even use it. Those who would be confused by it included.
This is a case where it's useful to move into a separate mode for just one type of app. Why? because by highlighting the newly-visible widgets and dimmming everything else, you can show them ALL with one operation. They're small and simple enough to fit.
That means you never have to hunt for the icon or name of the widget you want. Hit the icon or F12, and instantly any widget you commonly use is there. The fact that each is a different color--and positioned where you left it--further helps you get right to what you're after. It's as though the app IS the icon. You see it, and you use it, with no selection process needed--except to trigger Dashboard.
You COULD make such a system available to all apps... multiple virtual desktops is cool... but that would confuse most users I think. They'd have to keep track of which apps were on the dashboard (or the other desktop[s]) and which were not. May as well do away with it then--and lose the instant-access, instant-dismissal benefit which is the reason for Dashboard.
That benefit applies to small apps that you use briefly--not to all apps. Exposé provides what you need for other kinds of apps.
Put another way, multiple virtual desktops all alike would be a neat power-user feature--I'd love Apple to add that--but it would be a burden to many other users. It wouldn't be something they'd use. Dashboard, however, is easily usable and comprehensible to everyone BECAUSE there's a clear distinction between it and "everything else." (And remember that many of these things have long been separate--as panes of Sherlock.)
Again, I think this distinction here is NOT artificial. It's recognizing a distinction that already existed between "real" apps and "mini" apps, and makes something useful of it--something that understands how people think and work. Address Book, Calculator, iCal, Stickies... these are all things I launch (bounce bounce), use for a moment, and then use a menu command or keyboard shortcut to quit or hide. With dashboard, ONE operation can show ALL of them--and hide them again--more quickly, easily, and without cluttering my dock with "trivial"--but vital--apps.
I think people will easily understand and remember what's a widget and what isn't. Nobody will find themselves wondering... "Web browser... is that in Dashboard?" Nor will they look for the latest weather under Applications. The principle of "widgets" vs. regular "apps" is further made clear by using a different name... They're not "Dashboard apps," they're "widgets."
Dashboard also avoids cluttering my screen with little app windows (or menu icons) to do minor things like display weather or control iTunes. If you want full-fledged always-present apps for those things, you CAN still have them. But they clutter your workspace. I've always been of two minds about such things, from CPU meters to remote-controllers to weather banners.
Solution? Dashboard lets you have your mini-apps AND your freedom from clutter. Have your cake and eat it too.
Sometimes dividing things into different areas or functions makes things MORE logical. That's why we have a menu bar, window gadgets, AND a Dock. Each does its job well. You COULD pack all those things into one long menu, but it would be harder to navigate, and it wouldn't respect the way people work with their machines.
And of course, for those who DON'T work that way--who want the mini apps mixed in with the full-scale apps... Dashboard is optional
Work the way you always have, and get around via Expose and the Dock alone. Your regular Calculator etc. still exist, and will still have their uses--when you WANT to work with a mix of apps, or when you're doing something more intensive and not "in and out." Like creating new contacts, or using the Calculator paper tape for a long series of calculations. Those aren't quick--and so they're not what Dashboard is for.
Some will never use Dashboard, and nothing is lost by having the option and not using it. But I think a LOT of people will find that Dashboard saves them time and effort. That it fits usefully into the way they use their computer. I think they will even miss it when sitting down at a Panther or Windows system.