Using an application that lets you see image previews in the file chooser,
navigate to a deep folder.

Click on an image file. The preview appears on the right side, and the file
chooser is resized to accomodate it.

Now click on a parent folder in the path bar. The preview disappears, and the
dialog gets resized. The path bar is also resized, items that were visible
before are suddenly invisible, and (the biggest problem) the item that was under
your mouse moves to an unpredictable place (it may even become invisible
itself). It's surprising, annoying and means you cannot go back to the folder
you were visiting using the path bar.

This is especially annoying when you are in a deep folder : with the preview
turned on, you can see the whole path in the path bar, but as soon as you click
on another folder only one or two folders can be seen. Since there is no easy,
visual way to link the previous path bar to the new one, it becomes quite useless.