Their search engine has proved invaluable to me when I can't read all the letters of a name scribled inside of a cased image. Enter just the first few letters of a surname, and it will find all list all , ie, enter "broad" and you will get broad, broadfoot, broadfield, etc, etc.
I've found CWD's data to be very accurate, and it almost always provides more info than the NPS data. Very good info on units, casualty reports, even some soldier photos. Give it a $10 trial!