The fight filler in YYH was pretty freaking awful. Particularly all of those tone breaking Koenma scenes and all of those times they drew out Hiei's fights to pad out the episode (which defeated the whole point of him being such a badass). But aside from that Yu Yu was (mostly) great about filler.
Manga in general just has better pacing period though.
Unless we're talking about ONE PIECE!! AARRHGHGH!! It's even worse then Part 2 Naruto!
I really enjoyed the filler in Rurouni Kenshin that was just random single episodes about the characters doing stuff, but the "filler arcs" were terrible.