I've been wanting to have access to Encore's features for a long time, however, it is not available as a standalone program, so it took a while to be in a position to acquire it (must purchase Premiere Pro or one of the suites that include it)
Here are the features that, for me and perhaps other users of Premiere Elements, make it so desirable:
1. Can burn one's Blu-ray project to a folder and “You can play the program using a DVD or Blu ray software player and the directory behaves just like a disc, including having full navigational abilities.”
2. Can burn Blu-ray, DVD and Flash from one and the same project--no need to start over for depending on the desired output, as with some DVD authoring programs
3. No need to transcode “assets” that are already in Blu-ray format
4. Interesting requirement for those who begin their slide shows in an Elements Organizer, which can automatically adjust the length of the slides to the length of the audio: “Ensure that the audio and video durations match on all tracks on a Blu ray Disc project. If the timeline in your project has audio tracks longer than the video track, you cannot burn a Blu ray disc.”
5. Last but certainly not least: “Encore is designed to work directly with Adobe Photoshop to build and edit menus and buttons. You can create entire menus or elements for menus (such as buttons and backgrounds) in Photoshop and import them directly into Encore. You can also edit Encore menus at any time in Photoshop, and have the changes updated immediately.”
Source of quotes: Written tutorials available on Adobe's web site under the category Encore.