I've only ever been to the Bull Run battle field and all the surrounding area that it encompassed.
There besides the sadness, I had the feeling of wonder seeing the terrain and putting up with 90 degree heat and humidity trying to imagine what it was like to wear the heavy clothes they did and battle on that terrain.
I've not been to Antietam. I think I would feel similar to how I felt at Shiloh, just being overwhelmed by the numbers of men who died in such a small area.
There were no seasonal uniforms issued back then, were there? And no field showers, either. I guess it didn't bother people because they all smelled the same. :)
Ironic, isn't it, that Wesley Clark is announcing his candidacy on the anniversary of Antietam, where the federals were commanded by George McClellan who would run as a Democrat against Lincoln in 1864. May Clark enjoy similar success!