One thing that did not trigger much of a reaction in me when I was first reading it, that is a little surprising now, is the mention made of scattered farmers (Men) who lived beyond the Shire, to the east of it. By the time of Lord of the Rings, one gets the impression that past Bree there is nothing but empty wilderness and ruins (and perhaps the occasional troll or three). Bilbo seems to be seeing more of a gradual decline in population. Does this mean I am misinterpreting or misremembering what is said in LotR, or that something (e.g. trolls and other predators) has cleared this region of the last vestigial remnants of human settlement between The Hobbit and LotR?
The trolls themselves, also, are feasting on mutton. One does not usually picture sheep wandering around in the wilderness to be caught, and it is interesting that it is not venison that the trolls are feasting on, or any other wild animal. Were there sheep-herders in this area, perhaps extinguished by these trolls (and perhaps others like them who wandered down from the Ettenmoors or Misty Mountains), or else convinced to move along to elsewhere?
In both of the first two chapters, the dwarves have showed up one or two at a time. They do not naturally seem to stay together very well. Also, what was Thorin doing, sitting in the rain and the dark, waiting on his last companions to come report to him? Thorin is unquestionably brave (he sees three trolls and his first thought is, "I am going to kick these guy's asses for mistreating my people"), but it is not clear that Thorin has the wisdom to be a leader (this is a repeating theme for him).
We get the clear impression that, at this point, Gandalf did not think he could just walk in and kill the three trolls, and he had to use the subterfuge of mimicking voices. Would he have been able to, if they had begun to carry out any of their various plans for cooking the dwarves? He was not Gandalf the White, here, and in fact did not even have Orcrist yet. Still, it is hard to picture a Wizard getting beaten by a few trolls. I suppose part of the reason is that he was clever enough not to charge in like Thorin did, when there was the possibility of another way.
Speaking of Orcrist (and Glamdring and Sting), it is intriguing to wonder how swords of Gondolin could be here in the trolls' hoard. Perhaps they ended up at Khazad-dûm somehow, and then orcs from Moria who fled the war between Dwarves and Goblins were caught in turn by trolls. Thorin's people don't seem to have any memory of having once had such swords, however. Or, a dragon from the Withered Heath had it in their hoard somehow, from far to the north in Morgoth's fallen fortress of Angband. However it ended up in the trolls' cave, it was suggestive of a long tale untold (like a lot of things in The Hobbit).
Chapter 3