sorry to be the dissenting opinion here, but i don't think a tabbed finder is that great of an idea. tabs aren't on in safari by default because, believe it or not, they confuse some people. you show some people tabs, and they look at them like some kind of voodoo and proceed to switch back to ie and open up 3000 windows. stupid, i know, but the tab metaphor would likely be even more confusing in a file browser. the sidebar, expose, and spring-loaded folders solve most of the problems with this. tabs in the finder would likely be more confusing for newbies and may actually end up getting in the way without people realizing it. i certainly don't think that the os should be dumbed down for people who can't find the close-window button, but even as a tab-activist, i don't think finder tabs would be as useful as they are in browsers, chat clients, etc.