I'm surprised so many people have completely missed the point of Coverflow in the Finder. Maybe it's because Apple has called the Finder a "NEW" Finder. Sadly it isn't. But the addition of Coverflow could be one of the most important changes Apple has ever made to OS X.
Look at iTunes. We now know that there may be over 500 million copies of iTunes out there. If you ignore multiple downloads I'm betting there are still at least 100-200 million actively used copies. Now, the current iTunes has Coverflow. Anyone with iTunes knows how to use it because it is dead simple. Now, Apple can go to any iTunes user out there (the Windows using kind) and say "Look, if you can use iTunes, you can use a Mac." That is a very powerful thing.
There are lots of people who are scared of switching over or just don't think they want to because of a perceived lack of comfort with something new (in this case, OS X). Apple can further remove that barrier now with Coverflow. Does it mean every switcher will use it? Of course not, but it helps convince people to make the switch. Right now, Coverflow is one of the most important announcements to come out of WWDC, not because of the tech behind it or the usability, but because of what it means to new switchers. Apple can only sell more computers because of it.
Cover Flow is Pretty, but Fairly Useless