I agree with essentially everything said here.
There are a few writers in season 4 who also wrote in earlier seasons (Paul Tibbitt, Aaron Springer, Tim Hill, and a couple others), though indeed most of them are new.
I keep wondering why Mr. Lawrence doesn't write any more episodes, at least not season 4 episodes. He wrote a lot, especially seasons 1 and 2, and I remember really liking most of the episodes in which he was a writer. I say this because he's obviously still with the show as the voices of Plankton and Larry (and Plankton actually has more of a presence in season 4 compared to seasons 2 and 3.)