Just finished reading it and I fucking loved this manga.
The only complaint I have is that storytelling gets a lot weaker in the last arc, when the Angels and Daimon are introduced, and I didn't enjoy much the way Fujisawa handled Sho's and Daimon's motivations (Sakurai having a scar for saving Daimon felt ass-pulled to me). I also think Miyabi's last conflict could be handled a lot better, but I'm okay with the way it was done.
I also enjoyed the fact that the story isn't just about Onizuka being a teacher, but also about people learning how to live by their mistakes and children being children while growing up.
This could be an easy 10/10 if it wasn't for these last 5 volumes falling short for the incredibely marvelous rest of the series, but its greatest qualities (such as the character writing and development and the way Fujisawa used all of it to creat context to debate more serious themes and reinforcing the plot with this social commentary) remained there until the very end and I have to give the props to it.
Overall, despite my complaints, this is one hell of a fucking good ride that everyone should take. 9-9,5/10 for me