As to your first point, I can't recall the last time I've seen a corrupt OOXML format document, and I deal with a ton of them daily. The old binary format files were a much different story.
Here you go. See anything wrong with those styles on the last screen grab?Yeah, same here. We used to have occasional problems with binary formats, but the only time we had any issues recently was a couple of years ago when a virus managed to get in and bork a few folders on the file server.
We don't get this all that frequently, but it does happen. I have a collection of before and afters. Also, that the XLCleanerDotNET4.0 exists and only works with XLSX is a testament that I am not alone and certain problems happen with the XLSX OOXML format frequently enough that a programmer created a tool to fix the issue.