TV and Kids? I 'd like to hear a few opinions and ideas - Thanks

How much TV should kids watch? When should they watch it? What alternatives are there? - my kids pay attention to the TV and follow the stories - I try to choose stations with no adverts and programes suitable to their age. It just gives me time to cook, clean etc. It gives them a bit of down time too. Perhaps they watch 2-3 hours in a day. What opinions are out there?