Well said, Cadena! You've hit upon nearly everything I discuss with my students when beginning the novel. The only thing I can think to add to this discussion is that fact that while most firemen appear to be nearly emotionless, or at least not overly passionate about anything, Montag takes a unique and perhaps unusual pleasure in doing his work. I believe this sets him apart from many of the other firemen, except for his captain. Also, it shows that his ability to experience true passion will be his downfall in terms of his fireman career; when he becomes disillusioned with what he is doing, he needs to find something else to consume him. In this case, he decides to search for the meaning held within books, and plunges into a secret society of individuals who dedicate themselves to the preservation of books and their all-too-important messages.
The opening scene serves several purposes. One is to simply provide a setting for the story; it is a good way to introduce what Montag does and what their society is like. It also provides an attention-getter, a hook to gather the reader's interest. Using such stark phrases as "It was a pleasure to burn", "Montag grinned the fierce grin of all men singed and driven back by flame", and "this great python spitting its venemous kerosene upon the world" really sets up a dramatic image, and a pretty intense attention-getter.
A last purpose for the opening scene is for the reader to have something to contrast against the Montag that eventually turns against his profession and society. In the opening, we see a man who loves his job, who went to sleep with the "fiery smile still gripped by his face muscles", to a man who quakes to burn someone's house, who steals books, who plots a subterfuge of the laws of the land, who takes Beatty's life to preserve Faber's, and who ends up an outcast, and one of the few left to rebuild civilation. When we see that new Montag, and contrast it to the opening scene, there is a stark difference, and provides the scope of his change.