I just thought of something funny. The final IE8 released today will probably surpass Opera's cumulative install base over the years in just a couple of days (or less). And that's without 1) being shipped in an OS (Win7 is coming out later, the beta is a very small share), 2) not being installed in automatic or forced updates or 3) whining.
The beta of IE8 already has almost 2x the market share of Opera.