Tabbed browsing has already been taken up by IE, so that's not such a big plus any more. Play around with opening links and closing tabs with mouse gestures. It's only implemented, rather clunkily, with add-ons in Firefox, and AFAIK not at all in IE. Also, get Task Manager up to monitor resource usage, and load up something big in Opera, and see how much resources it uses. Then minimise Opera, and check the figures again. For sheer efficiency of browsing, nothing equals Opera.
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