We stayed in 1 day for taking an exam. Since our plane is quite early, we arrived at the hotel before 6 am. Although we have heard that there's a early check-in policy that we can pay $25 for it, we were told by a staff with poker face & unfriendly attitude that there's no room for us to check in early.
Fortunately, the staff arrange use to stay in a nearby hotel (Aqua Suite) to rest (we paid for it for $77), and we went back to Days inn for check-in at 3 pm. The Aqua was clearly not as good as Days inn, and is definitely not worth to spend $77 for staying just a few hours. So if you would arrive early, I would strongly recommend you to book Days inn for 2 nights.
The hotel is an ideal place for preparing an exam. It's not far away form test center (Bank of Hawaii); taking a taxi costs less then $25 (if you take a round trip and negotiate with the driver; you can get discount). There is a drinking fountain in the first floor and a big local supermarket just across the street, and McDonald is also nearby. However, please don't walk outside at night since it's not a very safe area.
The biggest drawback of this hotel is definitely the terrible sound insulation. The wall is just like paper and you can hear lots of noise from outside the door, from the window, and from the next door, so I would suggest you to bring earplugs with you. You will definitely need it if you're here for a test.