Bount arc: filler, why the fuck would anyone watch this?
Arrancar arc: yay training. Has some awesome moments (Ikkaku bankai, for instance), some boring moments, and some funny moments.
Heuco Mundo: The first half of this arc was boring as shit. Kubo realized this and made the second half into Orihime-in-bondage, FUCKING-INVINCIBLE MAN takes on the world, and Kenpachi being awesome.
Winter War arc: Well, it looks cool so far, but we're, like, two chapters in.
Negative chapters: Ditto previous comment. (he's switching back and forth between the Winter War and an Urahara and Aizen centric flashback.)