Turner recruited 5,000 Civil War buffs to re-create the battle scenes (and he used them all for Pickett's Charge),and generally did an amazing job. The only real problem with the production is Martin Sheen's turn as Robert E. Lee, who he portrays as either being drunk or more than slightly nuts.
It's interesting that they just started running trailers for Gods and Generals, also being made by Ted, with many of the actors from Gettysburg reprising their roles. It's going to be about Stonewall Jackson. Apparently they tried to get Sheen as Lee again, but he couldn't do it because of his West Wing commitments, so they got Robert Duvall instead. I'm not going to complain.
Also, the music they use during the TV ads for Gangs of New York was originally written for Gettysburg. It bugs me somewhat when they steal music from movies to promote other movies.