Show/Hide Controls is fairly important, particularly for new users who aren't aware of the Ctrl+K hotkey.
Domain of Definition (DoD) is useful for troubleshooting and optimizing a composite. Getting to it through the context menu is cumbersome.
I use the Normalize button frequently for quickly viewing some auxiliary buffers—Z and World Position almost always have values outside the 0-1 range. Also for checking detail in super-white areas.
Pixel Aspect Ratio correction and Smooth Resize
might be okay to leave in the context menu. I do toggle Smooth Resize frequently, though.
I also miss the seldom-used pop-up button for choosing the active control widget. But since I might be the only person who even noticed it was there, I can see why it wasn't a big priority to keep.

Could we get back the feature where clicking the name of the displayed tool above the Viewer selects it? The widget's already there; might as well make it functional.