Lovely house in a beautiful place! Not a luxury resort, but if you don't mind a little effort to get there and don't need to be waited on... Casa Dulce is a wonderful place to relax and get away from the world. The house has everything you need (except laundry) to just be and enjoy the beautiful surroundings. The house is on a beach on the bay side of the Osa. You can cool off in the ocean, or in the pretty little dipping pool just off the porch. Relax with a good book in one of the comfy hammocks and you will be visited by colorful birds, monkeys and the friendly local "jungle dogs." (Seriously, they are friendly and not a bother.) Erik the caretaker is nearby and extremely friendly and helpful.
If you want some adventure, there are many nearby tours of all types that can be arranged... just keep in mind that the drive to and from the local town, Puerto Jiminez, is a bit rough.
I would definitely recommend Casa Dulce and would stay again.