I love Jesse in this, you need him to provide that contrast to Walt, and his role in the drug world. You need a man like Jesse, more of a street character who can provide that link to the underworld, plus he plays his role perfectly. I think the chemistry between those two has been fantastic. He does twattish things, but is it any less then you expect from him?
I like how he has grown as well, from the first episode to where he is, how he has coped with his setbacks, but it's a transformation which doesn't have an end in sight, you think he is growing into a better, complete person and that's it, and then he's back to square one.
I've never in my life seen the range of facial expressions, and just facial expressions used to express a point, or a line...It's unreal. The Wire did this very well at times, and at times over-did it, but there is something mesmerizing about Walt.