1. The Anime and the pathetic filler arcs. This isn't realy fair since the anime shouldn't be compared with the manga.
2. The Time- skip: The art changed alot and not in a positive manner. The arcs seam repetitive and kinda boring ( fight/training/new technique/fight/.........).
3. The new characters. They just don't have the same charm as the old ones had exept Atsukagi)
4. Sai: He just sucks.
5. The whole Sasuke left us buhuhuhuhu. Get over it.
6. Sasuke. Many people just hate him and think he's overpowerd
7. The fights: Still very good in my opinion, but some find them too long.
8. The lack of character developement: Now this is something I realy don't mind, but most characters havn't changed a bit. Even after the time-skip.
9. The whole story is very predictable. mostly one knows whats gonna hapen in the next 3-6 chapters. You know the outcome of every fight befor it realy starts.
10. The lack of a gripping storyline. The whole story is very simpel and forwards, whithout any major plottwists or surprises. The only secrets you want to know are about Atsukagi and their goals/ abilities.