I just now realized I didn't give an opinion on the season overall, now that it's finished airing.
First and foremost, the animation, yes, it's difficult to adjust to, considering the series was traditionally animated for so long, and the Flash animation does seem a bit stiff and robotic at times, but I'm sure overtime, 9 Story will improve, though that does remain to be seen.
Secondly, I'm glad that for the first time since Season 8, Arthur's voice DIDN'T sound like D.W. (and D.W. didn't almost sound like a chipmunk), that makes it more tolerable to watch compared to previous seasons, though as I said previously, I think the fact that both Mr. Haney and Miss Turner (Miss Turner especially) both sound like they're dying when they speak is another little tell-tell sign the show's gone on a little too long.
I still haven't gotten to see Ladonna and Bud's debut episode, so I can't really give too much of an opinion on the characters' addition to the cast, let alone, decide if they really serve a purpose being on the show or not (most people I've heard don't seem to think so).
As for the episodes overall, they were hit or miss, there were some really great episodes, and some not so much, but overall, this is a very decent season, the first decent one we've had in ages.