He's rather interesting in the sense that he is the most notable, perhaps even the only, character in the books that seems to be really working class - other than Hagrid, but in Hagrid's case, obviously other characteristics are more prominent. Most of the HP characters are middle class or even upper class like the Malfoys, but with Stan, Rowling apparently decided to make an exception. He and Hagrid get their working class accents, whereas nearly everybody else in the series seems to speak basically standard British English, albeit with some regional accents perhaps. Stan serves here - and again on a few occasions in later books - as an illustration of what the man on the wizarding street thinks, so to speak, rather than the better-informed and more than averagely intelligent characters at Hogwarts. The Daily Prophet's influence over this silent majority of the wizarding world becomes clear here (perhaps it's been clear before? I don't really recall that, though), and it's a telling sign that Hermione mentions in her letter that she's begun reading it.

On a completely unrelated and rather irrelevant matter, it's somewhat strange that Rowling says the Bus can't go over (sea)water, then adds that it moves from Anglesea to Aberdeen. I suppose it can go over seawater if it is narrow, and bridged besides?