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At this point, this is nothing more than another "me too" sort of post, but I like it. I can agree that there is probably more whitespace than needs to be, but I don't find it distracting. I'm fairly indifferent on "position: fixed" elements on a page, so I can't relate to the out-rage over the header and sidebar. I can copy & paste into text boxes again, so that's a plus. As for performance, if there's any kind of "comment auto-loading" based on scrollbar event firing, see Learning from Twitter by John Resig. I haven't personally experienced this yet, so this may not be the issue at all. Anyway, definitely an improvement in appearance.