Ok here is the breakdown
Story
What i like the most is that the manga recognizes that lesbianism is still not accepted by the society. At the beginning the girls deny their feeling for each other and dismiss it as strong friendship.
At one point Mari even dated a boy to convince herself that she is straight. Even when they are officially a couple, Mari hides it from their friends because she fears of social alienazition and critism. In my opinion this manga managed to capture the real problem faced by couples like Mari and Akko so i give it 8.
Character
It's not a story about cinderella meeting princesses charming who is the most beautiful, popular and the richest girl in school. The two leads, mari and akko, are just two ordinary girl, none of them looks like a man (bishounen).
The characters also graduate to next grades, they don't have time to be idle ponder and day dream. The characters evolve because the clock is ticking for them and they are forced to make important deicisions. 8

Art
The artwork is nice and consistent , it's also quite detailed unlike other shoujo ai that don't have any background at al, it's plus point to mel. After finshing Girlfriends, i browsed for other Milk Morinaga's works and to me this is by far her best art work. 8

Enjoyment

I still read again, because i enjoy the artwork and the story 8