I've read just about everyone's comments on Directory Opus and the general feeling is that 4.0 is the best.
In my TOSEC Applications set (I haven't updated to the latest...if there was an update), there are 2:
Directory Opus v4.0 (1992)(GP Software)
Directory Opus v4.12CU (1994)(GP Software)
Which one is best? Is the CU one cut down in any way? (I have that issue of CU Amiga, but haven't used the coverdisk in years, so I can't remember what it's like)