Personally, I would strongly suggest watching the films in order. While "56 Up" does provide some recaps, the cumulative effect of the series is built by watching each age in depth.
The 'Up Series' represents one of the most fascinating and unusual uses of film in cinema history - a documentary life-long chronicle of the lives of 14 people starting at 7 years old, revisiting them every seven years through age 56 (so far). While I could quibble, wishing for a bit more depth here and there (especially with the women, where there's a bit too much emphasis on love and marriage at the expense of all else), and by nature the later episodes sometimes have to speed through more than would be ideal,since they have to both catch the audience back up as well as moving the stories forward, no matter. It's really an astounding, moving, frightening and uplifting document. There's no way to watch this remarkable series of films without reflecting deeply on one's own life, and how you have changed (and stayed the same) over your own lifetime.
While Michael Aped deserves every bit of credit he's received for this amazing piece of cultural anthropology,it's important to note the first film, 7 Up, was actually directed by Paul Almond, and Apted was a that point a researcher for the project.
This new episode is as excellent as it's predecessors, revealing more surprising twists in turns as our group heads towards the end of mid-life, and stare into the realities of old age. Some old friends re-appear, some have continued in directions they had been going in, and some have changed course yet again.
One thing that's interesting, and more present in this episode than earlier ones are some of the subjects questioning the objectivity and 'reality' of the series. There are interesting cases made that what we, the audience, sees isn't the truth of who these people are, but only a created character. It also (by proxy) makes one reflect on how much being in these films has affected the lives of the participants. Just as in physics, it seems to be true here as well, that the very act of being observed changes what is being observed.
All fascinating and thought-provoking stuff.