Safari 4 Beta's new tab arrangement has me bothered. It seems to be largely lifted from Chrome's user interface that puts the tabs at the very top of the window. Not only is this a departure from Apple's typical UI choices, it presents problems for users with special needs.
On your average Apple user interface, every object -- a title bar, menu, button, or handle -- has a single function. It can resize the window, move it, close it, or scroll it. Safari 4's tabs, however, have a dual purpose: They not only can be selected to move the entire Safari 4 window, but can be clicked individually to display their contents. In Safari 3, this was handled by two different objects -- the title bar to move the window, and tabs in the tab bar.
Google chose to put tabs at the top of the window because it was an important part of the user metaphor for their web browser, Chrome. In Chrome, tabs are independent processes brought together in a kind of stack. This is all very well and good, but it poses the same problem of having the area at the top of the window do two things at once: move the window as a whole, and control each item in the stack.