For me, labels are very useful : they are a way to store info about a peculiar file without having to open the file to make a decison over again about the value of that file. For instance, I use labels to classify files as :
- to be backed up
- to use for client A (or B or C...)
- to keep for every client
- to discuss with the other team members
My only problem with labels is that there weren't ever enough (it has stayed the same since system 6), so it has always limited my use of the concept.
Since I am far away from my Mac, I still have not used OS X (sob !), so I do not know if these limitations still apply (I would think they do).