Adobe already supports GPU acceleration on certain Lightroom functions in the Develop and Library modules. However, the app still has a reputation for being doggy, which has prompted many users to switch to alternative products, particularly Capture One Pro.
With the new release, Adobe is promising a smoother and more responsive editing experience, especially if you're working on photos with several adjustments on a high resolution monitor (4K and up) with a powerful GPU. If you have a relatively slow system and 1080p display, though, you probably won't see much difference.
Adobe has added a few other features, like the ability to batch merge images used in HDR, Panoramas and HDR Panoramas, PNG exports, color labels for collections, and speedups to the Library module. For Lightroom CC, the stripped-down version that lets you save images in the cloud, Adobe has introduced a function that lets you recover accidentally deleted images. The updates are now rolling out (I've received it in Europe) and for more information, check out Adobe's August photography blog.