There is a reason Mitsuru Adachi's mangas are more often then not given a good critique.
He doesn't give his mangas the gold-digger treatment by overly drawing the plots out.
1) It ended just as the main premise of the story achieved a conclusion.
2) It achieved a suspension of judgement with the audience on the plot.
4) It didn't give you the time to realize how much of a bitch Suzuka really is.
5) It didn't give you the time to realize how much of a bitch Suzuka really is.
6) It ended on a note that allowed the bastard Yamato to remain cooler than the other side of the pillow. (To the extremely disillusioned at least.)
7) It doesn't create any unnecessary questions while reaching a conclusion.
Just as MojoMunkeez says...
It was good. Leave it like that.
Even the best things starts to diminish if they are overly drawn out. (Economic principal of diminishing marginal utility of sorts.)
I can see a couple of OVAs produced after the manga finishes for character screentime and plot epilogues but I wouldn't want anything more.
There's always the manga for those who have a drama monkey on their backs...