I used to be able to move the canvas around with Spacebar+click when the canvas wasn't breaching the confines of the UI/Screen. I can still move it around with this method if the canvas I am using goes off screen a bit (like it's too big to fit the whole image in...then it lets me).
I like to move the canvas around whenever I want, even if I can see the whole thing, so that I can put the particular part of the image that I am working on in the place on screen that my eye most easily meets....which is typically right in the middle of the screen. As of now I must either blow up the canvas bigger than I want it to be, in order to arrange it how I see fit with space+click, OR, I have to just settle for wherever on the screen Adobe deems fit to put my canvas.
Anyone know what happened to the ability to move my canvas around, if it DOESN'T take up the whole screen/UI?
If you press "F" to enter "fullscreen mode with menu bar" you can drag the canvas about as you will and still have access to your tools. I think you may have had this functionality in standard view in much earlier versions of photoshop but I don't recall ever seeing it myself.