http://labs.adobe.com/technologies/lightroom/

Here’s the skinny:

Lightroom Beta 4 also features:
-Groundbreaking changes in the way tone curve adjustments are made and displayed, giving you the highest quality results in an interface that’s easier to use than ever before.
-More streamlined and elegant user interface – We’ve made several changes to the look and feel based on your feedback in the earlier beta releases.
-Customizable interface – You can now display only the controls you want to be visible.
-Precision white balance selection tool
-Facility to easily rename and convert files to DNG after they’ve been imported to the Lightroom library
-Increased interaction between Lightroom library organizational structure and the underlying file system
-Filter and search presets to more quickly find the photographs you want
-Better performance and improved interface for the Web module features
-Develop control improvements based on community feedback, including comments from the Pixmantec user community (welcome!)

So I guess it is getting close:

There is a limited amount of time left for you to give us feedback on the Lightroom Beta project, so please continue sharing your opinions with us on the forums.