I've gotten used to double-clicking the thumbnails to open images in the viewer. That's easier (doesn't require moving the mouse and finding a 'next' control that's only visible on hover) and allows random access. The only problem is when the thumbnails are hidden by the viewer. But then the viewer closes with one click, so that's not a big deal.
What I would like to see a full edit-mode set of controls on hover of the viewer. That would make it much easier to open an image in the viewer for purpose of checking it's quality or suitability, then immediately deleting, replacing, moving elsewhere, etc. This would save a lot of time where the thumbnails are too small to accommodate the controls.