There is so many different views of Lincoln and his presidency that this should be interesting to see the take Spielberg has on it.
I think the picked the perfect person to play him. Daniel Day-Lewis is probably the best actor of the A or B list who could play the role.
Tommy Lee Jones is perfect to play Thaddeus Stevens, both in looks an attitude. Stevens was known to be a first class bleep. He and his fellow Radical Republicans did more harm to this nation and pretty much set up the US political system for more than a century. Lincoln wanted the South to be treated kindly and not punished for the Civil War. The Radical Republicans did, and upon Lincoln's death, got their way. Imagine how it might have been if Lincoln had lived to implement his vision of Reconstruction.
Jared Harris was good as Moriarty in the latest Sherlock Holmes, so I suspect he'll go well as Grant.
Can't stand Sally Field, but I'll give her credit, she's a good actress.
The real question is who is going to play John Wilkes Booth. He is still not listed, but all evidence says it is likely Michael Stuhlbarg.
John Williams is doing the music so it will undoubtedly be good.