I have to say, I didn't think I'd ever find a use for the dahsboard, and thought it was a silly idea when I first heard about it, but now I find myself using it VERY often. It makes sense as a place for things that you only need to reference or look at every once in a while, but would otherwise be a waste to dispaly on screen all of the time.
iStat Pro is pretty ubiquitous, and I use it. The calendar is also there on my dashboard, as well as the weather and weather radar, calculator and stocks.
And for what it's worth, Windows Vista's sidebar (which runs "gadgets") is a poor subsititute, primarily because it runs all those little things you only want to see once in a while, but the sidebar never goes away when no longer needed. It just stays there, taking up valuable desktop space. And is evidently more of a memory hog than widgets ever was.