OK, I cheated....too curious. It definitely sounds good, and I'm glad you didn't try to sound like Lennon with the vocals and the slap-back, etc....
Your version is a lot slower, though, which makes it drag a lot, especially since you don't have other instruments coming in like the original. The part that Chambie's talking about IS different. You're doing a descending thing with your left hand. There should be something climbing, either on the right hand, or both hands, but it's definitely not the same.