As a scriptwriter, I understand some of the concerns of Walsh, Boyen, and Jackson. However, I still would have stayed closer to the book and not have made some of the adaptations they did. I would have handled them differently.
I think the WiKi should have met Gandalf at the door on either a horse or a the hellbeasts. I think the change made both Gandalf and the WiKi appear weak and inconsequential. I think closeups of their hands since they both hold Rings of Power might have established them as nearly co-equal and created more of a hightened tension.
I think Faramir should have had some mental anguish over the ring but not left Ithilien with Frodo and Sam. Leave it to Frodo and Sam to establish that Faramir is a better man through those actions. However, I think I would have kept the Boromir/Faramir/Denethor scenes in Osgiliath.
I don't think the there should have been too many changes made to the plot. Tolkien's plots were sometimes plodding, but didn't need to be changed. Simply adding detail in some places and letting other parts go without comment could have sped things up to a fast pace without alienating fans of the books. Other parts could have been referenced in montage segments. Personally, I think the best way to visualize the books would be with a single 20+ episode season
Et tu BAUT? Quantum mutatus ab illo.