Another good thing missing in the READ ME is the fact that you can now change the track for a Marker. You do it from the Marker Window, right-click on one or more and select change track from the menu.
Now on to the more "limiting" functionality of the spanned markers not mentioned in the blog:
1. They cannot be tied to a track such as V or A, etc.
2. They represent a span in time and locked to time, and will not move with content as you edit.
3. If you add more TC tracks in the timeline, you see the same spans there, visual overkill
3. You can turn off Markers in the source/window navigation bars but that also turns of the ability to read the Marker in the overlay display.
As it stand for me, I will find very limited use for these on the record side, but can see using it on source clips as a quick reference to preferred areas of a take. And there is so much more it can do, we shall see if Avid updates it over time.