Always nice to see people solve their own problems, a couple of tips that perhaps you found on your own. I have modified the Polar Plot.vi and Polar Plot Data.vi that are in vi.lib (make your own copy!) I like to change things like line width and add markers for the points. If you look inside Polar Plot Data.vi you will see the array of points which feeds the Draw Multiple Points.vi, in my copy I have created an indicator and pass these points back out through Polar Plot.vi so I know the picture coordinates of the data points. Then I can draw circles or triangles or whatever at these coordinates, or decimate for markers every n points. You can use these same coordinates to draw your text box with some suitable offset. Probably saves a little trig on your part, not that it is a bad thing.
I tend to like my plots uncluttered, and if I want coordinates in a picture based plot I have a crazy event-driven scheme to pop-up the coordinates when the mouse is in the vicinity, but otherwise leave it alone. If you like labelled points and want to convince others that it is a good idea for LabVIEW I would (1) post a screenshot so we can decide if we like the look and (2) post the idea on the LV idea exchange. Personally, I think the beauty of the picture based plots is that they are blank canvasses, the downside is that the user interactions are limited to what you explicitly add.
I would like to see a polar plot on the same footing as the XY graph, cursors, annotations, events, etc.
