It's a fairly mediocre title, with a lot of ideas that don't go anywhere or are settled in a non-respectable manner.
I'd say if
Clannad had the best characterization and development of a KEY title, and
Kanon the "least bad" when it came to magic resolution, AB is worse in both respects.
The comedy was perhaps the most overdone. I had enough high-school hijinks in Geass, thank you very much.
More episodes like the guitar girl were needed, an episode focusing heavily on one person's development and getting that person to move on, with slight development between Kanade and Otonashi to make their relationship just a bit smoother.
I think Yuri was probably counter-productive for this; instead of introducing the series
in media res, she should have come a bit later, and woken up Otonashi as he grew accustomed to Purgatory. The two of them making the dead aware, then Otonashi having a change of heart, would have been more satisfying development I think. Yuri's "plot dumps" were lazy and destructive to the narrative and mystery of the world, I felt.
Easily my least favourite Key-
related property, but then again even
Ever17's writer didn't have a lot of luck with anime TV either, right?