This hotel set an "equator" of our trip in all means. The trip was planned from highly active with stops at eco-lodges on the Caribbean side - to tranquil with some beach time at the pacific resort. I would say this is the perfect place to set the base if you want to explore Arenal area, especially if you driving. Location wise I would divide Arenal area into 2 parts: where you can and can not see lava flows. So from Casa Luna you have a great view of volcano and can see eruptions but will not see lava. But you are right next to the waterfall, within walking distance from La Fortuna (~25 min walk) and withing short drive from some active attractions like canyoning with Desafio company. It is about 24km drive from the lake Arenal - great spot to see lava flows and hanging bridges park and about 7-8 km from hot springs (it is on the way to the lake). Some local people recommended to use the place across the street from fancy Baldi springs resort. There is ton of other attractions in the area.
The hotel itself made a very pleasant impression. Nicely decorated, quiet. The pool faces the volcano and you can hear its rumblings about every 2 hours. You can see the eruption in the clear sky. Very reasonably priced restaurant (as I found out later on the trip) has a good menu, I'd go for the fish though. I would say you can it 3 course for $30-$40. This is the only place on our trip that had stable hot water. Elsewhere you got all cold or all hot or unable to mix it to the desired temperature - here we were happy. There is a free laptop with internet to use @ the counter. Our room had TV, condition that we never used and fridge. Staff speaks english. There is a parking area which I believe is free. I found all prices to be in US$. And you loose money if you pay in colones due to a higher rate at least that was a stable trend for us up to the point when we got to the pacific side where all was vice versa and extremely expensive.
Bottom line - I would recommend this place to anyone. This seems to be a good place to stay whole week and get the most out of the area or stay just 1-2 nights before the next hop.
p.s. we were offered a taxi for $20 to go check the eruption in the evening from the lake side. I heard one of the best places to see eruption is Arenal volcano lodge.
Walking in La Fortuna appears to be safe. I heard the same from both guides and local people. What a great characters can be met here :)