Positive and or negative things about the maps you can find in the arena mode.
I feel like you are asking this question a tad bit early 
Positives:
This is Halo. New forged maps will be added to playlists.
Arena wasn`t in the beta?
The maps in the Beta were awesome. Especially the Midship remake and Empire were my favorites. I´m curious how the other maps will hold up.
I have a good feeling about the maps. Really enjoyed the beta and free map updates cant be bad 