I stayed at Luna Llena with my girlfriend for 3 nights in mid August 2012. Of all the places we stayed at in Costa Rica, this had by far the nicest layout. Nestled in the hillside, it really feels like you're part of the jungle, especially when the monkies come running across the roof. Like others have said, its nice to be away from the loud party places downtown, but still be only a 5 minute walk to them and the beach (I hope you don't mind walking uphill). The rooms were nice, we stayed in the dorm one night and then room number 9 the other 2 nights. Cleanliness was great in the rooms, the bathrooms, and the kitchen. Security was also great, we stupidly left our wallets out on the nightstand in the room and even a bunch of cash right next to them but they were untouched when we came back (and it was obvious that the rooms had been cleaned). We did accidentally leave shampoo in the shower room and a half bottle of rum in the lounge area overnight and they were gone in the morning, but we kind of expected that. Milly, the owner, is very sweet and accomodating. Overall, if you're in Montezuma, go here. cheap, chill, and fun.

The best parts: The orange and white cat, the architecture, the fact that it is not a crazy party place, and Julio, the Friday night security gaurd!

The drawbacks: There are ants (big red ones) in room #9 but they never bothered us (there is a mosquito net over the bed for extra security), the fact that the lounge area closes at 10pm.

We enjoyed our time at Luna Llena. We cooked in the kitchen, and enjoyed talking and sharing with other guests. The room was adequate, as were the shower and toilet facilities. The treetop setting was very pleasant--just be prepared for the uphill hike and many steps to the hotel.

A surprisingly nice place, friendly service, peaceful. Liked that it was far enough away from the town center that it was quiet (and there were monkeys!!) but that the town and the beach were still a short walk away.

I completely agree with the other enthusiastic recommendations for Luna Llena and there's very little I can add. I stayed in the shared dorm for three nights, $10 per night. The hostel felt like a home away from home. It was so comfortable and cozy, with really great decor and an absolutely unbeatable view. I woke up to howler monkeys each morning and watched the full moon rise during my stay. The Thursday night barbeque was such a fun and unique event - it really shows what a social and welcoming place Luna Llena is. Milly and the rest of the staff were so warm and helpful, I felt completely at ease.
After backpacking through Costa Rica and staying in many, many shared dorms, I can say without hesitation that Luna Llena is absolutely the best. Muchas gracias Milly y todos!