To me, here are the good aspects:
Battle scenes are decent, with the Sharpsburg scenes from Director's Cut in the cornfield being real good.
Uniforms and accoutrements on both sides are a BIG improvement over Gettysburg. Some farby outfits can be seen here and there, but altogether they get more right in that department than wrong. Though from what little I know of VMI headwear I expect the shakos worn in the Jackson funeral scene were made up.
Beards ain't as obviously fake in Gettysburg most of the time.
Background details are excellent most of the time
Just about all hats except the shakos during Jackson's funeral are dead on, and no cowboy hats, and isn't as bad as the headwear in Gettysburg.
Finally a real great touch in the Battle of Chancellorsville probably rarely noticed, most all the Union troops during the surprise attack are yelling and giving orders in German. A historically accurate touch most people don't notice. Funny part of it is when I was a kid watching the first time my very pro-Union Dad carried on that the movie likened the Union to Nazis and when Chancellorsville happened he exclaimed "Dad gum it! Now they have the Yanks speakin German like Nazis!!!!!"
The Bad:
The delivery of dialog, and a lot of the acting was HORRIBLE!!!!!!
It kept pumping up Robert Duvall playing Robert E. Lee, and baited folks into believing we'd get a lot of Lee scenes, and outright lied in the misleading.
The family scenes are a big case of "What in the ---- is this about and how is it relevant to the story?!"
Not enough of a balance on scenes, in other words very little Union in comparison to Gettysburg.
NOT ENOUGH WAR TO MUCH STALE QUIET SCENES THAT DO NOTHING FOR THE STORY AND NEVER SHOULD HAVE BEEN FILMED!!!!!
Promised more than it delivered in general.
Appently Chamberlain was a robust overweight person till I guess the winter of 1862? My God the Mud March and Union rations were bad on stomachs!
Probably a little too much bringing up slavery and Lost Cause notions. Now "Mr. Lewis" did exist, and accounts I've read of him have him as devoted, but from what little I've read he may have been a free man who volunteered for the job, but most Confederate accounts I've read mention him as a slave. But he does seem to have been devoted, after all the real Mr. Lewis was a devoted attendee of many reunions after the war. As for the slave mother and her children, I think they half-way did okay, I mean there is the dynamic of her being apparently very loyal to the family, but when they flee we see her espousing support for the Union and a DEEP desire to be free,
but the movie is WAY too subtle in showing this and completely undoes what it was trying to show by showing the mother and her children waiting on their owners to return when the Confederate Army returns to the city. They never should have showed that! They should have either shown her and her children running away as the Union Army retreats, or not shown them at all after her talk with General Hancock and thus implied they escaped. To do what they did they solidified the movie as a Lost Cause epic to anti-Confederate/Southern viewers for all time, when that ONE detail could have gotten the movie a little more, (but not much) respect.
NO SHOWING OF MCCLELLEN OR JOESEPH JOHNSTON!!!
Heck very little showing of Union Army commanders at all.
Too many folks a little too old for their roles, though I will admit most folks aged faster back then, I think they were still WAY overboard.
The Ugly:
The band playing "Bonnie Blue Flag" period! Especially the Hispanic women present I mean seriously! Just have soldiers in for the band and show everyone singing along and it'd be believable.