As far as I remember, it seemed that Jesse became less of a pussy in about the same proportion that Walter becomes more evil.

I think this is the best tv series I've ever seen. Fantastic writing, tight and engrossing plots, entirely believable characters (mostly, I agree about the bro-in-law till the last couple seasons) with each season getting better. They take a few liberties with the validity of the science but not much. Mythbusters did an episode on that aspect and had a lot of fun disproving some stuff. I don't remember what bit came from what season, so I would suggest not watching that till you finish with BB.