Menu customization is gone. I used it to set up more logical keyboard accelerators on right-click menus.
Visual indication of the auto crossfade status is gone.
Visual indication of the new project sample rate settings when no project is loaded is gone.
Polarity invert is gone from the track view, it's now in the inspector which is a usability step back for me--so ease of working is gone.
Many midi controls are gone from the track view and are now in the inspector, which is a usability step back.
Much of color customization is gone.
FX bins are narrower, showing less information. So information is gone.
Track View I/Os show less information.
From my point of view, while there are lots of terrific new features, and lots of old features are re-worked to work better, lots of items --
the little things, the polish, the minor things that make using the program just a bit easier-- are gone or made just a bit more difficult.
Out of the box, I'll agree that Sonar 8.5 and earlier versions had a cluttered, overwhelming appearance. But I was able to customize it into something very streamlined for how I work. X1 has lost a lot of that customizability.
I was talking about this with one of our usability designers where I work--a game company. I brought up my initial 8.5.3 normal template and then my best-of-my-ability X1 template. I pointed out all the various little differences and she agreed that X1 is a step backwards in those areas. I also pointed out lots of the terrific new features that are better in X1 like smart tool automation handling. From a purely graphical, informational, usability perspective, X1 has lost a lot. It's very frustrating to me.