It actually was terrible from a usability standpoint, but not by virtue of being on top. The proportional tabs meant that you never knew where to click to close a tab, and the fact that they really were at the very top of the window meant that you couldn't know where to click to drag the window around. Also, the ugly new tab button broke all kinds of Apple's own Human Interface Guidelines. Chrome's tab implementation is much better in these regards, although it still doesn't exactly follow the HIGs./QUOTE]
Very good points, I agree with them, but the evolutionary step would have been to fix these annoyances with a better implementation (even if they carbon copied chrome) not backtrack to a way we did things in the past, and for that not an inspired one with a whole lot of its own problems in implementation as you say.