If I had not purchased this set of tickets, I would have skipped Ambrosiana gallery. It is a gem! Two Da Vinci portraits that you can view up close and without being bumped around by a crowd. The collection of Flemish paintings was impressive. In particular, the Bouquet by Jan Brueghel is so extraordinarily stunning. Too bad the Raphael cartoon for the School of Athens was in restoration. However, seeing the restoration in restoration behind the glass was also very interesting. And The Last Supper ... because of the damages caused by the dry paint approach adopted by Da Vinci, the war/bomb and the exposure to elements ... It is probably just a skeleton of the original glory. But divine it is. I am amazed how vivid it looks today. a must-visit in Milan.
We got this package in order to get into The Last Supper, but the Ambrosiana Gallery was actually worth doing -- we were pleasantly surprised. There were no lines at the gallery, though, so we didn't actually have to skip the line. Both are definitely worth doing in Milan, though.
The Ambrosiana Gallery is a break from the tourist attractions -- it's worth seeing for the architecture of the building and for the library at the end with Leonardo's sketches. The Last Supper is obviously an attraction to see. You can get tickets for cheaper on the gov't site, but this was worth it for the limited time we had in Milan.