Having loved this show and watched it up to this point since it's premiere, I feel I should give my 2 cents on the matter.
Personally, Arthur is kinda like PBS' answer to The Simpsons, with the running out of ideas and whatnot. Plus the tolerance angle has gotten out of control.
Just put this into perspective: When the show began, all the main characters were pretty much your garden variety kid show kids, with the exception of Muffy, who had a Miss Piggy complex since day one. Now, they decide to make Buster's parents have a divorce, giving way to a interesting yet cheaply done spin-off, turn Francine Jewish, despite the fact she celebrated Christmas in an earlier episode, giving Binky a peanut allergy and a Chinese sister, not to mention the now obligatory Hispanic characters to shoehorn some Spanish into the show, and the most recent, giving MacGrady cancer.
I'm all for acceptance and such (That was one of the main themes of Fraggle Rock and Sesame Street, wasn't it?), but having EVERY SINGLE CHARACTER some different form of nationality or have some disability kinda disgusts me, seeing as the original seasons didn't make it an acceptathon.
As for plots, I can see them recycling plot ideas, but changing out certain variables to where it seems different (Like an episode with an embarrassing secret like wetting the bed or failing Kindergarten). Plus they hit some issues other kid shows would never touch (The Bleep episode, though to be fair, Tiny Toons did an episode about bleeps, but it was for one guy to get a girl, not so much stop cursing for his own good, but I digress)