I very much enjoyed Gohan's mini-arc during the Saiyan portion of DBZ. I felt like it was Toei's way of saying "If you still had any hope that the fun-loving monkey boy's son would be a chip off the old block, you can stop hoping now."
I also liked the Garlic Jr. arc for its way of showing how the Z-Warriors handle themselves without Goku, which I feel could have been exploited much better during the seven-year gap between the Cell Games and Buu Arc, to complement the Otherworld Tournament arc. A wasted opportunity, in my opinion.
I also like the addition of flashbacks, as long as they don't contradict the continuity (see Muten Roshi's original tale of the Dragon Ball).
Otherwise, I have a pretty negative outlook towards filler in Dragon Ball, with a few notable examples.
I hated the pre-22nd Tenka'ichi Budokai training arc. I simply found nothing memorable to it.
I'd say the same of all the filler in the Buu Arc. It either only served to drag out fights that had nothing really special to them in the first place, or to make power level debates more confusing today.









