I'm with J-bone on this one. I have seen a number of different changes in nomenclature. I actually began with CAS nomenclature, Beilstein, common, German, French, etc. During my stint with teaching, I was uncomfortable with IUPAC because I did not have a purpose in using it. However, the advantage that it has is that it is systematic. I began to compare common and IUPAC. By doing that, I thought I began to cover nomenclature reasonably well.
Which nomenclature do you use? It depends. I doubt many chemists could draw cholesterol from its IUPAC name. The IUPAC name is long. The kinds of names you are likely to find would be something like 2-fluorocholesterol. This combines the systematic name with a common name. The common names for many chemicals are more likely to be understood for large and unwieldy names. If you understand the principles of nomenclature, then you should be able to handle common, IUPAC, CAS, and many other names.