I think it gradually gets better until episode 20 or so, where it really picks up. Then I watched until episode 80 or whatever it was until the fillers really started... Still stuck there. Really depends on what you like, but if you like shounen/adventure/action I think it's a pretty good watch, the first season at least.
Filler arcs usually means made up, irrelevant things to the story that didn't appear in the original manga to start with. Reason for these can be that the anime is closing up to the original manga (and thus running out of source material) and tries to broaden the gap by making things up.