Since I've been using Simple UI, I've found I really like some of the features, though I prefer to work in Standard UI to have access to more options. I'd love to see many of the windows nestled together, like they are in Scene, but in Standard UI. (Real estate is important and I feel like I spend all day opening and closing windows to get them out of my way.)
I also like being able to quickly capture and see thumbnails of my Environments and Viewpoints and double click to activate them, rather than searching for an Environment in the Material Editor list.
Or... just combine these two UI modes and add on the extra options to Simple UI.