I would HIGHLY recommend the ultimate collector's set if only for the Partners in Rhythm DVD. It's kind of like a starting point or beginner's guide to becoming an Astaire and Rogers fan. It covers all the basics, but also has entertaining bits of information and interviews with people like Peter Bogdanovich, Ava Astaire McKenzie, John Mueller, Hermes Pan, and many others. All the other extras are very impressive as well. Some of the press kits had different kinds of articles over Astaire and/or Rogers that you might expect to read in a fan magazine from that time period. The photos were beautiful and glossy, and the CD had their most popular songs on it. It runs about 1 hour, 16 minutes.
Perhaps I was hoping for too much, but it'd have been nice to have a 20 song collection of their music. 10 simply isn't enough! (although all their biggest hits are there)
Haven't watched Partners in Rhythm yet - I'm still making my way through the actual movies. I'm doing it chronologically (although I skipped Flying Down to Rio).
But yes, the box set is really wonderful. Only two minor things are the DVDs are in slimcases (didn't really bother me, but might bother some) and the posters can no longer be obtained.