In what is now KDE tradition, this version 2.0.0 of KOffice is not yet on feature parity with the last release in the 1.x branch, KOffice 1.6. Several features that were part of 1.6 are not yet available in KOffice 2.0.0; in fact, entire applications that were in 1.6 are not yet here in 2.0.0. In the release announcement, the team states that future versions 2.1 and 2.2 will bring feature and application parity to the 2.x series. They have learned from KDE4's mistake: they state as clearly as humanly possible that KOffice 2.0.0 is not aimed at end users just yet. It is instead aimed towards early adopters and developers. Note, by the way, that said release announcement is riddled with spelling errors (what's their beef with the apostrophe?). I thought that was kind of funny considering its source project.
On to the goodness. KOffice 2.0 is the first release that takes full advantage of the improvements in Qt4 and KDE4, a task which took over 3 years to complete. Two improvements made along the way really stand out to me: a reworked and improved interface, and the concept of Flake Shapes. Since one of my prime interests has always been UI design and functioning, let's focus on the UI changes first.
Instead of just pumping out another Office 2003 UI re-implementation (like a certain other project insists on doing), the KOffice team sat down and designed their interface specifically for widescreen displays. Instead of using toolbars, they opted for placing tools in a sidebar. These tools can be torn off and treated as windows, docked on both sides, and so on. This brings some serious flexibility into the mix. While Office 2003 also supports dockable toolbars, which can also be placed on the sides, it doesn't look as elegant as what I'm seeing in KOffice 2.0.0. It feels like an afterthought in 2003.
Flake Shapes are basically clippings of a document which can be re-used in any other document in any other KOffice 2.0.0 application, providing good cross-application integration. "With Flake, any KOffice application can handle any shape. For instance, KWord can embed bitmap graphics, Krita can embed vector graphics and Karbon can embed charts." It also allows future applications to be created more easily.
KOffice 2.0.0 packages are already available for Gentoo, Ubuntu, and OpenSUSE. The Windows and Mac OS X releases are not yet available.