I agree about Jake Lloyd. It makes me angry that he gets bashed by so many people in the SW fandom. He was a little boy who played a little boy convincingly. He was not supposed to be creepy, but a kind-hearted enthusiastic boy. So I don't agree with the popular idea that Haley Joel Osmond should have been cast for "young Vader".
During repeated viewing of TMP I also realized that Jake integrates some of Vader's body language quite nicely, e.g. the way he sits in the speeder and is totally concentrated; how he tilts his head at times; how he points at Qui-Gon to emphasize his words.