Julia Roberts is surprising. The above poster is exactly right -- Meryl Streep is both expected and miscast. But if she plays it older, I'm sure she'll get another Oscar for this.
Here was my initial "dream movie cast" after revisiting the play.
Ed Asner = Beverly Weston (the Dennis Letts role)
Phillip Seymour Hoffman = Charlie Aiken (the Francis Guinan role)
Kathy Bates = Mattie Fae Aiken (the Rondi Reed role)
Ellen Page = Jean Fordham (the Madeleine Martin role)
Kevin Kline = Bill Fordham (the Jeff Perry role)
Jodie Foster = Barbara Fordham (the Amy Morton role)
Helen Mirren = Violet Weston (the Deanna Dunagan role)
Amy Adams = Karen Weston (the Mariann Mayberry role)
Diane Lane = Ivy Weston (the Sally Murphy role)
John C. Reilly = Steve Heidebrecht (the Brian Kerwin role)
Ryan Gosling = Little Charles (the Ian Barford role)
"The Spectacle has, indeed, an emotional attraction of its own, but, of all the parts, it is the least artistic, and connected least with the art of poetry. For the power of Tragedy, we may be sure, is felt even apart from representation and actors. Besides, the production of spectacular effects depends more on the art of the stage machinist than on that of the poet."
--Aristotle