: : : : 4) He can (apparently -- some people question this) enlarge
: : : : himself to giant size.

: : : Do people question this because they think it is a literary device rather than a physical change of form?

: : : I think this depends whether Tolkien actually states that that Gandalf seemed to grow to a giant size or whether he states that he physically grew. I can't remember.

: : That wouldn't matter, my dear Entish Istar. even if the professor wrote that "gandalf grew and filled the small room with his shadow" [made up quote], it would still be possible (indeed probable, IMO) that this is a metaphorical description. Meaning that from whoever's perspective, Gandalf seemed to - and therefore for all intents and purposes did - grow. Tolkien's writing is much more about feelings and impressions than actual physical, minutely detailed description.

: : Dave C-Q

: I very much agree with you...It is the intimidation og Gandalf's whole aura that makes him seem to grow (much like a low angle shot in the movies ;^) )

I would also agree with that. There are several instances in LotR where the appearance of a character changes (not just Gandalf), but in none of those instances did I believe that the physical body changed. One such example is in 'The Taming of Smeagol'. To Sam's eyes, Frodo appears to grow tall and lordly, while Gollum shrinks & appears to be a dog. This happens also at Mt. Doom, I believe. If Gandalf were the only one who got bigger, I might agree that his body actually grew bigger. But it is seen with other characters, so I take it as more of a 'vision'. With Gandalf, he projects the vision on purpose. With others, the vision comes unbidden (e.g. Sam viewing Frodo & Gollum).
-Steve S.