"PLUSES: Surroundings are gorgeous and lots of trails and things to do; full of birds for Birders, and various other animals. The staff was (mostly) professional, knowledgable and friendly. The grounds and rooms are very clean. The included breakfast is quite tasty with a variety of options.
CONCERNS: The property is isolated, as it is 40 mins w/ no traffic or road issues to La Fortuna and other activities outside the property. Some may love this. Dinners were more of a 3/5. Something I overlooked is that there is no air-conditioning, though this is on me for not realizing. During the warmer "dry" season we would have preferred air-conditioning.
PS: For all of the Arenal area (not just the Observatory) if driving from the West (say from Tamarindo beach area), once you hit Lake Arenal, it's about a 1 and 1/2 hour drive to the Observatory, and 2 hours+ to La Fortuna, and this is with no road issues and little traffic."