I usually watch all of a series, including filler. I watched all of One Piece except the Ice Hunter arc (I tried to watch it, I really did).
The major exception is Bleach. Some of the Bleach filler is just awful. I watched quite a bit of it, including the Bount arc, before I had enough and found a filler guide. If we're talking about episodes that actually bring the series down and make it look bad, then I consider skipping them to be beneficial to the overall experience.
Seriously, you'd have to pay me to watch another episode with that princess trying to play soccer.








