As a long time user of PD5 (PowerDesk) and for the last 3 years ExplorerPlus, I miss a few things when using Opus.
One of those is more icons such as
Single File Pane, Dual Pane Vertical, Dual Pane Horizontal, and Swap Panes.
They also have very nice Expand Branch and Collapse Branch icons.
The Pane icons are especially nice as I did not need to create Styles as I have to in Opus. True, Styles have more power to them but the Pane icons in ExplorerPlus were much easier and took up a LOT less space and got the job done.
I like a minimal amount of junk clogging up my screen and find icons take up a lot less space. I also like my menus, icons, and other items in one line across the top thereby providing the maximum amount of space for viewing files (after all, that is what a file manager is about is it not?).
Using more icons, and less Styles, allows me to achieve my goals of a single line as less space is taken up.