Hi!
AGEOD patch policy is in my opinion one of his bests assets. Their games are improving continually.
They patch a lot, fixing bugs and problems as soon as possible and also adding a lot of new things to the game.
I´m not sure what is your "out of the box" version, but if its previous to 1.08 patch (you can see your version on the right botton corner of the game load screen) you will find A LOT of new things: new buttons and options developed for Napoleon Campaigns game and retrofitted for free to the ACW game, new scenarios, better AI, improved map with more historical railroad net and many many tweaks and improvements.
I recommend you to patch as soon as possible and keep patching as new versions are posted.
Fortunately all the AGEOD's patches are compatible so you can keep playing the same campaign with new patches.
About “readme”, yes as you patch a looong readme doc will installs on your game directory. But I don’t think is available on the forums
If you want to take a look before installing i can attach my readme doc here when i arrive home in a couple of hours (i'm at work now :siffle
Regards!
EDIT: here are all the changes introduced until last official patch (1.09e)