When I was a kid, I remember watching Tom and Jerry with my dad and thinking it was a really funny cartoon. Now, that I'm much older, I'm really horrified by the cartoon. Now don't get me wrong, I'm not one of those people that goes around saying TV makes kids bad... blah, blah, blah.
But all the same, the violence and meanness of this cartoon are way out of proportion. I think it's the meanness that bothers me more than anything: the gleeful revenge, the evil plots to destroy the "enemy." I think the meanness is the worst part, actually. There's a lot of hatred in these stories.
So that's my take. I don't let my kids watch it anymore.