I have been tempted to look at the alphabetical listings of each edition and finding the 500 new words myself, just by brute force manual comparison. But, frankly, in my polyglot meanderings that just doesn’t seem to be the best use of my time. I think I will complete and revise this particular course to a certain level, review it manually with the 2nd ed. hard copy, and expand things with even more extensive frequency lists, such as the Advanced and Master lists in the Most Used Words series (which claims to cover the top 10,000 words, albeit from a somewhat different corpus). On top of that I can add my beloved collection for traditional phrase books and the various vocab lists in grammar books (as a functioning francophone I find Bescherelle is the best for me). It has taken me years to learn that crunching vocab is the most important thing I can do. As an obsessive, I used to worry about grammar rules first, and ended up knowing how to conjugate verbs without knowing many verbs to conjugate! It is far more ease for me to approach a grammar text with much more vocab under my belt. Simple concept, I know!