Saving Mr. Banks

Here's a link to the trailer on YouTube for Saving Mr. Banks, starring Tom Hanks as Walt.  The movie tells the story of the production and release of Mary Poppins.  The relationship between Walt and the author P.L. Travers was apparently not smooth and it is difficult to tell from the trailer how this will be presented.  One comment...Tom Hanks does not make a very convincing Walt Disney.  His diction and mannerisms look like someone trying too hard to impersonate Walt. At times he sounds a little like other characters he has played. Maybe this is just a first impression from the trailer, or maybe Hanks is just too well known to play Walt.  Casting mistake or misleading impression from the trailer? We'll see.