Once in a while I head on over to CS5 from Lightroom (I am currently on the latest version of LR) using the Edit In option. When I am back in Lightroom, I happen to notice a new EXIF field called Software. It says "Adobe Photoshop... om 4.0 (Machintosh). I am assuming the entire field reads "Adobe Photoshop Lightroom 4.0 (Macintosh).
Just being curious as to the purpose of this newly created field and why it is created at all once I come back to LR4 from saving in CS5. Thanks!