I just read this and thought I'd share it here with the rest of you who thought that the ending was rushed as it seems it might have been. According to this article (which references Akamatsu's own tumbler so it's probably true) he chose to end the manga because of disagreements with the publisher about the rights over the manga. This "neighboring copyright" law sounds pretty ridiculous so I hope he won't be alone in opposing this. It seems like something that's meant to reduce the rights of mangaka for no real reason so I really can't believe any of them could agree to this. (I also hope that if this is rejected strongly enough Akamatsu-sensei will continue Negima even if it's something like side stories about the rest of the characters at the end)
New Proposed Japanese Law the Reason Ken Akamatsu Ended "Negima!"?