The Explorer does have a map screen but no mapping capability.
You can import (from GPX) tracks and waypoints and view them on the Inreach's small screen. You can also create waypoints and routes in Mapshare and load them onto the Inreach. I find the map screen quite useful once it's loaded with tracks and waypoints. The pan and zoom works well and provides a good overview of your current location and proximity to your imported tracks and waypoints.
The only thing I've been frustrated by is the fact that waypoints that are transferred from the unit to Mapshare, can't be exported (export to GPX only sends the tracks, not the waypoints that I captured in the field). I've logged this as a bug with Delorme but no fix yet.
I agree, it would be nice to have a mapping display and I would love to see Garmin get into the game.