Facebook for the enterprise
After the new user interface, perhaps the next biggest improvement in SharePoint 2010 is the social experience, which centers on communities. My Sites go back to SharePoint Portal Server 2003 and are essentially personal sites where users can tailor the content.
In SharePoint 2010, users have far more flexibility in populating their personal attributes (profiles) with interests - and deciding how much of that information is public. Importantly, SharePoint exposes this public profile throughout the system - and therefore is the hub of an enterprise social experience.
Much like Facebook, there's a news feed, which helps community members keep track of the work their colleagues are doing. When you add keywords or tags to these activities, SharePoint becomes an even more valuable way to uncover, through searches, information about particular projects within an organization.
Social bookmarking offers another way to build knowledge within communities. Any piece of Internet content can be included in a community's set of bookmarks. Users can rate the content, and comment on the activities and contributions of others, much like you'd do with a blog post. I believe this feature is valuable in a business setting because the feedback is searchable, thereby helping find experts or information that might otherwise be hidden.
People search (a feature of the included search engine) connects with the social capabilities of SharePoint 2010. The system automatically infers expertise, which is mined from a user's activities. Search also takes into account "social distance." That is, if I search for someone with .Net experience, the search results will rank someone who's a direct colleague higher than someone in another organization.
FAST Search for SharePoint, a separate product, is highly recommended because FAST's faceted navigation lets you filter results by the names of people, places, and organizations.
Working with Office 2010
The integration story between Office and SharePoint improves greatly in their 2010 releases. The new Office Backstage view (available in all Office client applications), lets you do basic tasks such as check in and check out documents from a SharePoint library. Backstage also displays metadata auto-complete lists, such as the office locations that I created earlier.
What's more, users can work together as simultaneous co-authors on the same Word document. Word locks the section being edit by one person, while giving others editing privileges to the rest of the document - making for real-time team collaboration.