"Gollum will astonish, delight and move you - Cave Troll fans ain't seen nothing yet!"
"It is all looking up to, even beyond, the standards of the first movie."
Maybe so.
But, if he takes an active role in the battle of Helm's Deep (swordfighting, for instance) that would be a major departure from the book. Remember, Gandalf's role as a representative of the West was to encourage and organize, not take a direct hand in matters. He only stepped to the front when the Fellowship was faced with something that completely overmatched them, such as the Balrog and the chief Ringwraith.
I'll withhold further judgement until seeing the movie.