Yeah, I dislike the ending.
He could've at least made a time skip and showed Tsuna older and still a bit immature. But just to end it like that?
If it was a manga that was axed only after a few weeks or before it reached it's climax I would understand, but Hitman Reborn's been going on for eight years, and the only thing that really needed concluding was if Tsuna would become the 10th or not and which girl he would choose, (though it was pretty obvious,) Also I don't think the manga was axed, but the mangaka decided to end it, (could be wrong though) I guess she felt with her work on Pycho Pass she could afford to end Hitman Reborn.
Oh well the manga was one of my favourties for a while, up until the Future arc, when you have defeated the boss who ruled in all parallel universes except one, all other enemies would pale in comparison. Kinda like the problem seems to be with Bleach at the moment, after Aizen got defeated all other enemies seem pointless.