Bern Szukalski then turned to ArcGIS Explorer 900, mentioning that users would immediately notice the new ribbon user interface. He explained that it's not just attractive, but also very well-designed, and provides an easy and intuitive user experience, making Explorer ideal for providing broad access to GIS data and capabilities. Here's how it looks.
In 3D mode the features in the layer package were extruded, and Bern explained that this was because the layer package contained 3D features and had been created in ArcGlobe. In 2D mode, 3D features are draped flat. In 3D mode 3D features are extruded. This brought about a hearty round of applause from the audience.
Read more: http://blogs.esri.com/Info/blogs/arcgisexplorerblog/archive/2009/03/22/explorer-900-at-the-bpc-plenary-part-2.aspx