I think Ebert's comments that the temporal paradox discussions were missing himself missed the point. Here is what I think: The first terminator movie introduced the world of the future before the temporal ripples of the first T-101 mission altered it. In the original timeline, Sarah Conner would have had john and they would have lived happily with John dating Claire or whatever. But as soon as the T-101 and Reese were sent back the timeline was altered. By subjecting Sarah to the trauma of being hunted, the terminator actually created a future rebel in sarah. She began to fight against the creators of Skynet and trained John in advance of judgement day. This created a world where john knew ahead of time was ready. Something happened that made skynet create a new kind of terminator, maybe John's advanced knowledge of the future allowed him to determine better strategies against the T-101s. Thus the need for a new kind of terminator. Thus we have future 2, 1 being the unaltered one. Future 2's skynet again sent a terminator back, thus altering the future again. John befriends the T-101 and learns how to fight the T-1000. Thus we have future 3 and the basis for T3, where sarah dies of cancer and john is a renegade fearing the future. He is fate dto do everything despite what he does to prefent it which helps to keep everything rounded ( T3 is a prequel to the first movie in a way since the war is what started it all.) I am right in my hypothesis because of a scene in this movie where the T-101 says that he was sent to assassinate John because of his boyhood experiences with that particular model. Thus we see that the future was altered in a way since the Original john wouldn't have fallen for that trick, and probably won't in future 4 sicne the T-101 told him about it. Also a new terminator was created since John knew about it. The use of elements from both of the previous terminators was a good touch since they both had their advantages. So ebert is wrong, you have to find this stuff out yourself which is what I do anyway. I don't think there will be a fourth one since Arnold is running for govenor. But they don't need him anyway.
I enjoyed the humour in this movie as well. The spoofing of its own axioms was particularly good. The best was the strip club scene. The movie had to be different or else it would have just been the same, "come with me now! Run!" It did leave me with a feeling of despair at the end on behalf of John since nothing he could have done would have prevented that future. His only hope now is if the John of future 4 sends an agent back in time to stop the general from starting skynet. But that is asking for too much.