Great idea for any location it is available for. I bought a 2 day pass and later wished I splurged on the 3 day one as there was a free premium event, which we ended up going to after all. I used my 2 day pass for a one-day island tour which I only booked a day ahead. This was a great tour to get to know the lay of the land and see some spots where Oahu's history was made. I also went on a rain-forest, waterfall, and movie set hike at 9 am which left enough time to visit the palace in the afternoon. Both activities were well worth it. If you are intending to use this pass for one of the more popular tours, please book ahead. Many activities are booked up well in advance and while we were not using the card but trying to book direct, horse-riding or zip-lining were sold out for the rest of the week.
You really need to plan out your schedule in advance and make reservations well in advance in order to maximize this card. Most things close early so it's really only possible to do 2 a day. Not sure I would choose this option again. While we might have saved money, I think I might have preferred to spend a bit more to get higher quality events and have a better schedule.
This card is well worth the price! We were able to attend 3 or 4 attractions. Do NOT bypass the Pearl Harbor tour or the Oahu in one day!