Went there last month with my wife and really enjoyed it - the food (I use salsa lizano on everything I can now), drinks, and especially the people, are great.  We stayed at the Hotel Mangroove Papagayo and really enjoyed it.  If you want to play the points game, it is a Marriott Autograph property and a steal at 35,000 points/night.  Although not an all-inclusive place, they offered all-inclusive on food/drink for $120/pp/day which made everything really easy - basically spent the middle of every day eating ceviche and drinking by the pool and looking out at the bay.
 
	That said, we got a driver/guide and took a 6a-7p day trip to Arunal (as suggested above) and it was our favorite day.  Did the hanging bridges in the Mistico forest, which isn't overly adventurous or off-path, but we got what we wanted with the exception of a sloth sighting.  All sorts of colorful poisonous frogs, a few vipers, birds, etc.  We walked down to the La Fortuna waterfall, which was beautiful but it's a lot...a lot...of steps back up.  I'm in my late 30s, ride the bike a few mornings a week for 10+ miles, and I was gassed.  There were a ton of people down there that had me wondering how they would make it back up.  After that we went to a place called EcoTermales Hot Springs, which is only a day location (no hotel) and it was great.  I would repeat that whole day again in a heartbeat.
 
	Considering the Papagayo/bay setup was less "beach-y" than I was expecting, and they pool was where I wanted to be, I would honestly look for a similar setup inland in, or close to, the rainforest ecosystem.  The area close to Papagayo/Liberia Airport was more dry forest.