@tbernard I like that you are replacing "Activities", but I don’t like the design. I find it to abstract.
On the right you have small icons which are really easy to read (battery, volume, wifi), this pile however is not very descriptive and if you have only two virtual desktops it looks a bit strange.

If you are in the middle of a greater number of workspaces it is more understandable.

This pile should be replaced by an icon showing a desktop IMO.