Yesterday, KDE released their first Beta release towards KDE 4.1 that is planned to be released on July 29. It's aimed for testers, community members and enthusiasts in order to identify bugs and regressions, so that 4.1 can fully replace KDE 3 for end users.
Lots of changes has been integrated in this beta release (it's not yet final as their TODO list is still being worked on). You might want to see the announcement on their official website.
Here's the KDE 4.1 Beta 1 Highlights:
- Greatly expanded desktop shell functionality and configurability
- KDE Personal Information Management suite ported to KDE 4
- Many new and newly ported applications