The thing I'm eagerly anticipating is the overall screen / image quality. I'm certainly not getting the phone for its inferior sound quality, or flawed TouchWiz overlay.
The overall image due to the combination of high nit brightness, high contrast, low reflection, decent DPI, double ambient light sensors (I can't believe Samsung hasn't marketed this feature. Did anyone know about this before DisplayMates mentioned it?). Interested in seeing how HDR video plays out even though (apparently) there isn't much of it out to experience on our phones at the moment. Interested in some of the camera effects (like the night time examples shown on Samsung's global site for the phone - linked below). Down the line I might go the route of picking up the Gear VR (although i expect with the eyes that close to the screen there will be pixelization). Being able to adjust the resolution down and save battery is appealing, but the question is how much blurring or pixelization is going to occur when switched down? (Unless I'm viewing a high resolution video or photo the max screen resolution seem overkill, and a wasted use of energy).
There may be a few surprise features we don't even know about yet. There are a surprisingly large amount of features that Samsung hasn't mentioned, and some may simply be ignoring. I didn't know about the two ambient light sensors, or heart rate monitor since Samsung hasn't mentioned them. (Some things like the heart rate monitor are probably old news since the feature has been on phones and watches for quite a while, and their true usefulness can be questioned). Anyone read/hear of any other features the phone has that aren't being marketed, talked, or written about?