I would have to say the opposite with regard to temperament of snakes in a rack system. While I admit a rack is the absolute best option if you want your snakes to positively thrive, all of my animals became more aggressive when placed in the rack system. They are not exposed to any outside stimulation, which is great with regard to their health, but boy when I open those tubs they come flying out looking for dinner! Even the most timid animal I have ever owned changed into a food driven monster in the rack. While that doesn't bother me at all, as I'd rather have an animal that will eat than have an animal that is passive and won't eat, that is something to consider if you are considering switching.

Granted, the rack makes maintaining ideal temp and humidity a breeze, and almost ensures perfect sheds every time, however, a well decorated vivarium with carefully maintained temps and humidity works just fine and lets you see your pet occasionally when they are not hiding under one of their hide boxes. That is not to say that putting your animals in a rack will make them aggressive, but regular handling is important to help avoid general aggression.

That said, your snake does not look as though he wants to bite you in that picture. More nervous and inquisitive than anything. Even if he hisses at you when you go to pick him up, that does not mean he is going to bite. It is merely his way of saying, "Hey! I'm not too sure about this handling thing right now. What are you and why are you touching me?" That will calm down with regular handling. He is still getting to know you, that's all.

Congrats on your new addition and welcome to the addiction!