This was a great series. It was imperfect, and some episodes were a lot more boring or uninteresting than others, but the good outweighs the bad. The writers do an excellent job of world building, the animation is awesome, and the main characters are all interesting.
This is one of the few cartoons that was able to stand on it's feet with the same strength throughout.
As good as it is, it does have it's faults. Sometimes the characters are in some situations that make for some boring episodes. I'd honestly have a terribly made episode than one that is boring to watch.
Even with its flaws, it's still a great show.