Harry Potter
and the
Prisoner of Azkaban

Apparition and Other Travel

In books 1 and 2, we've already encountered travel by apparition and by floo powder. However, in book 3 it becomes important that people (namely, Sirius Black) not be able to get into Hogwarts so easily. Hermione explains that apparition cannot be used inside Hogwarts or on the Hogwarts grounds, and dementors are placed outside monitoring all entrances. No such restriction is suggested for travel by floo powder in and out of Hogwarts, but this method of travel is ignored (in fact, in book 4 Sirius actually uses floo powder to appear in the Gryffindor area, so he could have used it to gain access directly into the Gryffindor area in book 3).

We already know that the ban on apparition within Hogwarts does not apply to house elves, since Dobby has been able to apparate into and out of the hospital wing in book 1. House elves remain free to apparate within Hogwarts at will, even in book 6 after additional security methods are implemented.

In book 4, we first encounter portkeys. Portkeys provide another means of instant travel, and they work within Hogwarts. One is used to remove Harry from the grounds and to return him there at the end of book 4. Dumbledore uses them on more than one occasion to transport Harry and others in or out of Hogwarts.

In book 6, side-along apparition is introduced. Side-along apparition could have largely replaced floo powder travel for many of the episodes in the earlier books. Why wouldn't the Weasleys have used it instead of floo powder in book 2, for example?

Harry's Broom

In book 3, Harry's broom is destroyed by the whomping willow. It seems very curious that nobody was able to restore the broom. In later books, the reparo charm is used frequently to restore things that have been smashed to bits. In book 6, Dumbledore and Slughorn take almost no time at all in restoring Slughorn's home, which Slughorn had totally demolished just before Dumbledore and Harry arrived.

When Harry gets his Firebolt, it is taken away from him for a couple of months while it's completely dismantled to check for jinxes. In book 6, Filch has a sensor for sending dark objects. Seems like it should be possible to check for jinxes very quickly without dismantling the thing.