When I updated Calibre the last few times, I didn't read the updates and bugfixes list like I usually do, so I was shocked and very pleased to find the option to use custom column data in csv catalogs. You have no idea how happy this makes me! I can now fully use my Calibre data the way I need to.
Sorry, everyone else probably already knew about this being added. All I know is that last week I was thinking that Calibre would be perfect if I could do that... and now I can. I figured it deserved a gushing pronouncement because it takes the power of Calibre and further unlocks it to be used in other ways. To me, this is a very big deal.