Who or What is Tom Bombadil?

[Sardy]

One thing that strikes me as a bit odd about Tom is that his "power" seems limited to The Old Wood. It would seem that is he were indeed "the spirit of Middle-earth" or some such, that his presence and affect would be a bit more wide-ranging...

[Thalion]

'He is'

I have always read this as a "studder" on the part of Goldberry, not a definitive statement that "He is." Mind you, "He is" is followed first by a comma, not a period [Granted for grammatical sense it must be a comma, but Tolkien could just have easily wrote "He is." if he wanted to without any "said Goldberry" at the end...] Therefore I have never really affixed much to this statement in terms of reading it in similarity to God's claim in the Bible of "I am."

Additionally, if Tom MUST be catagorized, I deem him to be an enigma, purposefully one who doesn't fit with story. He doesn't represent an entity that can be defined by the terms of Middle Earth...also given the fact that he wears big Yellow boots (which in my mind look like giant rubber rain boots), Tom I believe is not meant to be understood..."He is" a mystery, on purpose with no equivocations...

EDIT:

It seems that she is saying He is what he appears to be - he doesn't wear a 'mask'.

I would concur...it would be the equivalent to seeing a purple elephant in the LotR...it is exactly as you see it...it has no underlying meaning, it wears no mask, it is as you see it; it has and needs no explanation...