The worst deviation from the books?

I guess you are mentioning that scene when Aragorn 'dreams' about Arwen dying... the jewel (the light of the evenstar) that Arwen presented him falling from his grip and shattering on the ground? Well that is not exactly Aragorn's battle with Sauron through the palantir. In fact this portion is not mentioned in the book at all. Do you agree with me?

In the original story , Aragorn refused to enter the city before a certain ceremony , this is important in my opinion ,it represents Aragorn coming into his own .Also ,the prophecy that" A King's hand are healing hands " was never mentioned , it is one of the signs of Aragorn's true descendence .

The omission of the Old Forest, Tom Bombadil, and the Barrow Wights didn't bother me that much either, because if you look at the plotline linearly, that whole sidestory is a linear "hiccup". It did nothing to advance the plot and in the outside world nothing progressed either - the Nazgul couldn't sense the Ring and probably just established a perimeter patrol in the zone where the Ring dropped off their "radar" and up to a day's walk in any direction. This situation could have been kept up indefinitely, or until the hobbits left Bombadil's protection. So I agree - it is probably one omission that made sense across the board - altho an old purist like myself would liked to have seen it anyway.

I tend to agree, The Rising of the Shire is one of my favorite chapters from ROTK, I hated to see it cut. I disliked that they cut Bombadil out, but I understood, however like you I feel that the Rising of the Shire is very important to the tale.