• Photo book creation – has become more popular and Lightroom 4 now has the ability to create photo books. These can be books for a client, to preserve memories, or just about any other reason that you want to see images in print. It is contained on a separate panel, and like the print module, it has a lot of presets that you can start with. Once you have completed your book, it can be printed to PDF or uploaded to Blurb Books for printing to hard copy.
• Location-based photo organization – gives you the ability to GPS track where your photographs were taken from. With many smartphones and GPS-enabled cameras that record the location data automatically, you can track your photos. If your camera does not have that capability, you can add by hand just by typing the information in the search box and applying the information.
• Extended video support – now lets you import and make simple edits without having to learn a separate video editing software program. You can catalog your video clips alongside your photos, organize, view, make adjustments and edits, play and trim clips, and extract still images from video footage. Video clips are handled like still images, so it’s easy to make adjustments so your clips match the look and feel of associated photos or reflect your own personal style.
• Soft proofing – lets you easily preview how an image will look on color-profiled printers— right down to the printer, paper, and ink combination—or in color-managed web browsers.
• Enhanced online sharing integration – now adds the ability of seeing the comments made on social networking sites appear back in your Lightroom library. You also have the ability to share your video much in the same way you have had the ability to share your photos in the past to social sites like Facebook and Flickr.
Outside of the added modules there isn't a lot of changes to the interface overall within Lightroom 4. You can, by right clicking on the module bar, turn off modules that you don't want to see, which is very useful if there is a module that you never use like say the slideshow. This could become more important in the future if more modules are added.