I've let mine all watch kids shows from a young age. They do pick up alot of stuff.
i have heard that parking them infront of the tv as a small baby has a worse affect, as the motions on a tv are too fast & it can affect the way the pathways in the brain develop.
I don't know much about it, but do have a friend who used to park her DD in front of the tv for hours on end (all day) from only a few weeks old & her DD was a much later developer than any of mine. Still is. But that could just be her too & have nothing to do with the tv