I would highly recommend this program for those who want something off the beaten path. Nagasaki is full of history, as the first port where foreigners first entered and where confined to helped to shape what it is today. There are so many historical sites around the area such as Dejima, the Dutch Island, Glover Garden; a colonial village where some foreigners lived, Chinatown, and much more. Because of the foreign influence, it also has some delicious food that is famous to the area!!
My favorite part was that since you rarely see any tourists besides your fellow students, you get more interaction with locals. Many locals were interested in talking to me when I was walking around or at the bus stop to ask what I was doing there since they don't see too many tourists there, and that was one of my favorite parts. Not as many people spoke English as you would see in bigger cities in Japan, but people were still friendly and you could communicate in broken English and Japanese.
The bus system around town does not have any English translations on the buses or schedules so you have to try to read the kanji or ask the bus driver where it goes, but I feel it is more authentic that way! During orientation they will tell you what kanji to look for if you want to go to certain places.
I felt the academics weren't challenging enough and really easy. I do come from a more rigorous school and major so I felt that way, but I know some students felt that some of the classes had a lot of work and were challenging so it depends on what you are used to at your home university.
I did a homestay which I HIGHLY recommend. I got to eat some of the best meals of my life that my host mom prepared and got to help with some of it. These were also meals you can't find at any restaurant. I also got to go on trips around Kyushu with my host family and got to do things most students weren't able to since we went to places that a lot of them didn't know about or that were hard to get to with public transportation. All of my fondest memories were with my host family.
Nagasaki is very beautiful but it is harder to travel to neighboring areas due to all the mountains and the public transportation system is not as developed as it is in other areas of Japan, so if you are looking for a location as a travel base I would recommend the other locations that are offered, but if you are looking for something authentic where you can immerse in the culture I would definitely recommend this program!