Lightroom 5 is now available!
I just finished my local upgrade downloading, converting, and installing Lightroom 5. By far the coolest features for me are the new healing brush and radial filter.
The healing brush is a separate tab, like the clone brush, under the Spot Removal tool. It works similarly like it does in Photoshop. The difference is that it allows you to paint the image, like remove a duck from her hiding place in the weeds, and then move the sample replacement area anywhere you want in the photo. This will control the precision of backfilling the area that once was the duck to make it look like the weeds never had a duck!
The Radial Filter will allow you to control the area and quality of vignetting if you choose to use this in your image. The Effects panel already present in Lightroom changes the image globally, whereas the Radial Filter allows for content-specific vignette filtering.
Videos and information describing these features and more can be found here.
You can download Lightroom 5 here.