The notable enhancements you will find in KDE 4.6.0 are as follows -
A new Activities system has been introduced in the KDE Plasma Workspaces. This helps you to demarcate your activities on computer into different categories like Work, Home, Recreation, Web browsing, etc.Dolphin file manager gets Faceted Browsing - This allows Dolphin to give you better search results by reading the meta data of files.KDE games have been spruced up. Gwenview (The image viewer) and KSnapshot (The screen capture tool) have received Social Networking capabilities. This means you will be able to share your snapshots and pictures to Flickr, Twitter, Facebook etc from within these tools.KDE in 4.6.0 gains "Mobile build target" which allows for easier deployment of applications on mobile platforms.
As of now experimental builds of KDE applications for various mobile platforms like MeeGo, MS Windows Mobile and Symbian can be found on the web but are currently unsupported.
With the mobile build target capabilities gained by KDE applications, this is bound to change for the better. 
You can read the official announcement from KDE for the full details.
And if you are itching to try out KDE 4.6.0, I would strongly recommend a Linux distribution which has a rolling release because these Linux distributions bring changes far more quicker than traditional Linux distributions which follow a 6 month release schedule.Arch Linux, and PCLinuxOS support a rolling release.
