The Book: Bilbo Baggins is still enjoying a smoke from his pipe, but it's much longer than the one shown in the film; it reaches down almost to his feet. The conversation they share is nearly identical, with a few exceptions. Bilbo initially offers to share his tobacco with Gandalf (who does not use any magic at this point in the story), and makes mention of a few other things Gandalf was known for in the Shire - like giving Old Took a pair of magic diamond studs that never came undone until commanded, and taking a bunch of other young hobbits on adventures. Gandalf indulges in a bit more wordplay about giving out pardons before Bilbo says his final good morning. But our eponymous Hobbit, too polite even when angry, can't leave without inviting Gandalf over to tea the next day... which he immediately regrets after closing his door. Gandalf scratches a sign on the door with the spike on his staff and walks away.
What does it matter? The conversation is word-by-word the same in most places, aside from a few cuts made for the sake of the film. The only substantial things left out are Gandalf's past dealings with the Shire, and Bilbo's invitation to tea.
My opinion: This scene did everything right. I'd have liked to see Bilbo invite Gandalf to tea, even when annoyed at the old wizard, just because I find his unfailing politeness to be an endearing, Hobbit-like quality. Little is missed without it, though. I am very happy they did not mention the magic diamond studs - such silly magic things added to the whimsical fantasy of The Hobbit, but never fully meshed well with the somewhat more "mature" atmosphere of the Lord of the Rings saga as a whole (a problem The Hobbit admittedly has in spades). As for leaving out the fact that Gandalf has been known to take "so many quiet lads and lasses" on "mad adventures," well... the less said about that, the better.
"Wanna come with me and a bunch of my hairy homeless friends? It's cool, I knew your mom."