The Mavic prop guard is one of the newer accessories being released. To me, it makes the drone look bigger. I like the fact that the Mavic is more indestructible as well. With the protection to the props, I like that my fingers are also protected from any unwanted cuts.
To be honest I've been saying for years that all hover type drones should have nacelles with no access to spinning props in flight, it just makes sense. You immediately do away with 80% of safety concerns that way.