Mark,
It sounds like the 'dot' is just a fancy check box. Correct?
Kirk, you might be correct. (The dots turn orange when selected.) In Media Pro I can select dots to display images for one or more Catalog Sets/Collections (using CMD-click) and then single click to highlight or manipulate an entirely different Collection name in the list while keeping my original (dot) selection intact. The dots allow the user to use single click to
either view images or manipulate the Collection list. Like I say, the best of both worlds. A contextual menu, opened from an icon at the top of the panel, allows you to change the dot behavior by toggling between "Union" (OR-style filtering) and "Intersection" (AND style).
[Edited for clarity/accuracy.]Media Pro uses this functionality for each of the catalog fields/metadata terms in its Organize panel (Catalog Sets, keywords, label, rating, etc.). I believe this design essentially allows for browsing and simple filtering without the need for separate Browse or Filter panels. More advanced filtering/searching across metadata fields is done with the Find tool.
[Edited for clarity/accuracy.]Oh, and the contextual menu for a Media Pro collection is opened by right clicking or Ctrl-clicking the Collection/Catalog Set name on the left (not the image). The concept is to add (or remove) the Collection/Catalog Set "term" to (or from) selected image(s).