Honestly i wish this series had as many episodes as naruto, as it really just makes the best out of each one.
The ending was alright, a bit predictable, and i am sad it actually ended at 15 episodes. Zetsoubo Sensei lasted at least 30. If anything it does seem a bit out of place. I mean really, if you had to make an ending make it somewhat of a happy episode instead of an episode 2/3 full of grey objects.
On a very related note, the prequel to Bakemonogatari is coming out. Idk when the anime is actually scheduled but i will definitely watch it.