I stayed at Mari's place for a month. Everything about the unit is great apart from the wifi (more on this below). The best thing about this unit is the location, being right next to the Ala Wai Canal and not too far from the beaches: 10-15 min walk to Fort DeRussy Beach and 20 min walk to Ala Moana beach/Magic Island. It is also at the edge of Waikiki which was perfect for me since I did not want to be in central Waikiki. Mari is a good host and was helpful with all my questions. The check-in/check-out process was seamless. The apartment is also very clean and had a kitchenette which was great. The bed was a bit uncomfortable for me. The building has a laundry but you'll need to buy detergent from the shop near the lobby (same goes for soap, shampoo etc. if you're doing a long stay).
The only thing that was a major problem during my stay: the Wi-fi. The wifi in the unit wasn't working so Mari suggested I use the network from one of the neighboring rooms while the internet company fixed the problem. The network from adjacent units was very unreliable as it kept dropping randomly, this was a problem since I was planning to work from Hawaii. After this solution didn't work Mari provided me with a portable wifi device. This helped but it had a monthly usage limit so I ended up mostly relying on my phone's hotspot. Also, the internet company people never showed up during the month I stayed here. I heard from other tenants that the internet is actually a big problem in this entire building (Hawaiian Monarch Hotel) so keep that in mind if you're booking here as this building houses a lot of AirBnB units from different hosts.