I have been working with the beta 2 release of SharePoint 2010 for a few weeks now, and just today realized what I was seeing: the Global Navigation tabs now wrap when there are enough top-level sites that they don't all fit across the width of the page! No more scrollbar when you start to have "too many" sites!
When I think of all the client requests I received about this, and the custom development I saw implemented to achieve it, I'm very happy this is a feature of the new version - although the dark side of this is that folks may now be tempted to leave good Information Architecture principles aside and build top-level sites to their hearts' content. I think the dreaded homepage scrollbar of MOSS 2007 was a major factor in keeping top-level tabs to a minimum, as well as keeping the names of those tabs short and to the point, neither of which is a bad thing. With more freedom to build and name sites without the penalty of making the page too wide, site admins may be tempted to stray from the generally recommended 4-8 top-level tabs and potentially cause usability problems (especially if drop-down navigation comes into the mix).
But enough governance. Global tab wrapping is a seemingly small but often-requested piece of functionality that ultimately makes SharePoint 2010 a more flexible tool.