It might be a good idea to add the Mark/Unmark back to the context menu as well. We omitted it since the menu seemed to be getting awfully long, but it'd likely be a good idea to put it back. (You never really know how much some features are being used until you try omitting them from a version!)
-Pete
It's still there:
1. Select the items by highlighting the whole row (dragging from the left-most column)
2. Use Edit > Mark (Ctrl+R), or Edit > Unmark (Ctrl+U) to mark the issues
Depending on your column setup, the Marked column may not be initially visible: if so, you can add it using the tip here: