I use the shipping tags primarily now. I have also numbered all my kegs, and before the walk-in was built, I had kegs stored in different parts of the basement, so I also kept an excel spreadsheet of my inventory, what was in the keg by number, as well as last known location. Now that everything is in the walk-in, I don't use the numbers any more, but for a time, they were extremely useful for me.
I've thought about using the numbers again with the excel spreadsheet, just in case something happens to the paper tag, but I have realized I'm just too lazy to do that much book keeping. I do have to be careful though, as I have nearly 80 kegs with something in them in the walk-in, and some kegs are stacked three high in there, so I am not entirely sure of what all I still have in there. Haha.