How many fucking references to Lord of the Rings do we need? Or does Peter Jackson think this is something that actually happens?
Gollum comes screaming through the hole in the wall, but, unable to see Bilbo, continues on his search for the hobbit. Bilbo follows Gollum all the way to the exit, where he sees Gandalf and the rest of Thorin's Company making their escape. However, Gollum is in the way; even invisible, Bilbo wouldn't be able to make it past without alerting the dangerous creature. Bilbo readies his blade for an easy kill, but, seeing the look of utter despair on Gollum's face, finds himself unable to go through with it. Instead, Bilbo opts to try and leap over Gollum. He makes the jump, but his foot strikes Gollum in the face, alerting the creature to his presence. There's nothing Gollum can do about it, though; defeated, he shrieks his hatred for Bilbo Baggins.
The Book: Gollum promises to help Bilbo find his way out, but first, he needs to get something from his hut in the middle of the lake. Bilbo waits impatiently as Gollum takes his raft across the water; he doesn't know that Gollum intends to fetch the ring in order to kill Bilbo with it. Gollum can't find the ring, however, and begins to shriek about having lost the precious. He again asks Bilbo what the hobbit has in his pocket, and begins to paddle wildly back to shore. Bilbo turns and runs. His hand find its way into his pocket, where the ring accidentally slips onto his finger. He trips, and when Gollum runs right by him, realizes he is invisible. Bilbo follows Gollum, who starts to argue with himself. He watches Gollum navigate through the mountain to the way out. Fearing goblins, however, Gollum decides to just wait at a narrow passageway. The only way out is past him. Bilbo weighs the option of killing Gollum; pity wells in his heart, and he decides not to. He instead leaps over Gollum's head. Gollum screams how he hates Bilbo Baggins, but is too afraid of goblins to go any further.
Whatever. Not like we'll ever see this guy again.
Bilbo follows the passageway until he sees a leak of sunshine from an ajar door, guarded by several armored goblins. The goblins attack him; whether by accident or some evil trick of the ring, it was no longer on his finger, and Bilbo Baggins was no longer invisible. He quickly puts it back on, and as the goblins swarm around to look for him, he hides behind a barrel. Even invisible, he's afraid one of the milling goblins would bump into him. He eventually runs to the door, but it's too heavy for him to open. He tries to squeeze through the crack as the goblins realize that something is casting a shadow. With one last burst of energy, Bilbo squirms through, bursting off the buttons of his coat. He's escaped.
What difference does it make? In the end, both versions of events largely show the same things: Gollum tries to attack Bilbo; Bilbo becomes invisible and follows Gollum to the exit; Bilbo decides not to kill Gollum, then jumps over him and escapes. There are a lot of changes, though, some of which really do start to add up: like the omission of Gollum's hut, or the goblins at the end of Bilbo's escape. At a certain point, Peter Jackson is no longer telling Tolkein's story, but his own.
My Opinion: I was really disappointed to not see Gollum's little hut in the movie. I can understand the desire to streamline this whole scene - cutting out the goblins near the end was probably a good idea - but that little detail could have provided a cool visual, as well as given Gollum a little bit more depth. I'd liked to have seen where he sleeps, what sorts of things he's got stored there, etc. For the most part, though, I was happy with Bilbo's escape. The burst buttons I was particularly looking forward to. It's a good mental image that always stuck with me, years after reading the book for the first time. I don't think it matters if the buttons burst at a different time; it's the fact that they broke off at all that mattered.
Hobbits are fat: now an important plot point!
The only change that may have been important is the "trick" that the ring pulls on Bilbo. It's important that the One Ring's malevolent intelligence is hinted at so early on. This attribute is entirely missing from the movie. And I don't really understand the need to have the ring fall on his finger like it did with Frodo. Is it really just an attempt to shoe-horn another fucking reference? If so, I think we're at like 80 references to the original movie trilogy. It wasn't a necessary departure from Tolkein's writings, and actually pulled me away from the story for a few minutes.