I am a newbie to DOpus, and I am quite impressed, for the most part. There is one usability issue that I had not figured out how to overcome, and I did not find any hint in the Help system: it is great to be able to do flexible selection of multiple files in a Folder Tab (Power or Details mode); each click simply adds the file to the selection. However, what I cannot figure out is how to CANCEL the selection of X files and start again; Escape button does not do it; any insight ???? 
Easiest way is to right-click the toolbar button to the right of the parent button. The one with the hand holding a piece of paper. (Left-clicking it will select all files, right-clicking deselects all.)
You can also bind the command to a hotkey if you want.
Another option, if you have a 3-button mouse, is to set the left button to behave the same as in Explorer (so clicking a file or somewhere empty will deselect all other files unless shift/ctrl is held down) and setting the middle mouse button to do toggle selection (so you can select multiple things without having to hold ctrl down). In fact, this is the default behaviour of Details mode but if you never thought "what happens if I middle click some files?" then you might not notice it. 
Thanks a bunch. Your response was timely and very helpful, and it even worked 