Browsing and editing are all done in full screen mode making the most of my 15 in MacBook screen.
In browsing mode I have the tool bar showing with browser button selected and all other buttons on the top right deselected. This gives me the folders on the left and the rest of the screen full of thumbnail images. Then when I select an image for editing I press the top right edit button. Once in editing mode I hide browser, hide thumbs, hide toolbar and then go fullscreen. When editing I have just the image and editing tools on the right. This is when it would be nice to have a border around the image. Basically I use 2 workspaces to maximise my available screen. It would also be nice for the app to save the workspace when closing so that on re-launch you are back to were you were.
Hope that gives you more of an idea.