I would choose this apartment for the next time as well, I think this already tells a lot.
The apartment is well equipped and spacious. we just used the lower floor because we were only 2 with my girlfriend but it is big enough for a family with 2 big beds and 2 bathrooms. Regarding the bathroom it is just super, big, clean, huge mirror. Free internet and local telephone calls. Huge balcony, enough for a whole family.
Starting from Princeville we discovered all north shore beaches, the lovely town of Hanalei and did snorkeling an hiking on the miraculous Napali coast. We also drove through the Waimea Canyon and the Southern part of the island.
I also recommend the Blue Hawaiian helicopter tour because using a rented car you can see only 10% of Kauai! Seeing it from above was an unforgettable experience.
We also went to the Smiths Luau, well... I have been on better one in Oahu in the Polynesian Cultural Center... there were too many people, not the best show, not the best food but the place and the park around it is large and beautiful.
The people in Kauai are very nice, sharing Aloha. :-)