Unfortunately this particular piece of dialog doesn't allow much in the way of subtext or changes. he says what he feels and there are not really any emotional changes. So in terms of acting, its hard to do anything REALLY interesting other then what is obvious. having said that,. the only suggestions I think I can offer on this piece is that the lip-sync feels just a little bit off. It might be a good experiment to make the audio play a frame or two later. I understand the filmic reason for cutting away to the other characters but sometimes when the principle character is NOT talking is the best opportunity for the acting.
I guess the main thing you could ask yourself with this piece or if you are moving forward on another is "what is it the character is NOT saying, but is feeling and thinking" And show THAT! It will be far more interesting. And I think for that you need context, a situation. I think your work is good, there is not much to say technically, just think of the "story" for the next one. and what is the un-obvious and complicated emotion or idea that you as the animator can simply communicate?
Hope that helps!
Also check out his tutorial for 3D World;
If you guys got anything else to critic just post it up in the comments, I'll be refining this entry.
Happy New Year 2010!