Included in this release candidate is support for new cameras including Canon 1200D (T5), Fujifilm X-T1, Nikon D4S, and Phase One IQ250 to name a few. This is actually exciting news since they are releasing support for cameras that hasn't even hit the market yet. In the past, new camera owners were quite often out of luck for months if you wanted to use the new Raw file formats from these cameras with Camera Raw or Lightroom. If you wonder what that subscription money is doing for you, this is a good case in point. Well done Adobe.
Also new in the release candidate is a new collection of lens profiles including the iPhone 5c, FujiFilm x100s, Nikon & Canon lenses and a bunch for the Sony Alpha. Again, good news they are getting caught up quick on some of these newly released cameras.
There's a couple of new features too. A new side-by-side comparison of before and after versions of your processed photo. Pete Eye correction has also been added and new function in the Radial Filter as well as better controls for the local adjustment sliders.
One other interesting feature is the added Camera Profiles for the Fujifilm x series cameras. If you're a Fuji camera user like I am (x100), I'm sure your well aware of the great JPEG processing you have available from your Fuji camera profiles. Well now you can use those same type profiles with your Raw files too. This must mean Fuji cameras are definitely making a come back and getting more popular than ever.
They are also signalling the future with the dropping of support for Photoshop CS6 for a few operating systems such as Windows XP, Windows Vista, and Mac OSX 10.6.
Release candidates are well tested beta versions that Adobe would like input from a larger community on its performance. Any feedback should be made on the Adobe feedback portal.