Large lists change from SharePoint 2007 to 2010
SharePoint 2010 is more than just SharePoint 2007 plus a bunch of new bullet points on the box. We didn’t just haphazardly build a bunch of new features, look back at the fertile seeds we planted, and muse about how “everything should work pretty well as libraries get large.” We built, and more importantly, tested all the features you’re reading about with scale in mind. We are setting new scale targets for 2010 that go above and beyond what we set in 2007. These numbers are not final yet, but we're shooting for tens of millions of documents in a single library, depending on some specific parameters of your scenario.