I've now made it through Vol 4 and it was another great job by Fox. The print quality on these films is very good and TREASURE ISLAND in particular looks near pristine. I was also impressed at the improvement of HONOLULU and RENO from what I remember seeing on AMC.
Loved the featurettes. Having the local experts discuss things like Reno and the SF World's Fair/Treasure Island made it all seem more real. The color footage of the real Treasure Island is not to be missed. There's also an interesting piece on the real Zodiac killer from the 60s/70s; there is still some speculation that the killer may have been influenced by the Chan film.
This is my favorite set so far. Treasure Island and Reno are probably my two favorite Chans.
By the way, I have a small collection of memorabilia from the World's Fair on Treasure Island. I was influenced to acquire them partly because of the Chan film (and a couple of non-Chan mysteries that are set there).