Points well taken on MA area beaches. Playa Espadilla (outside the park) as well as Playa Espadilla Sur (immediately inside the park) are the ones worst known for the rips. Playa Manuel Antonio and Playa Escondido, appropriately enough meaning hidden, or what you and most others refer to simply as beach#3, are both in horseshoe shaped coves. This makes their waters far calmer, although I WAS flipped once when I tried to land there in a surf kayak (let me know if anyone ever finds my prescription sunglasses

). Actually, in those areas I'd be more concerned about striking my spot under a beach apple or machineel tree

. Swimming aside those ones inside the park are definitely some of the most beautiful beaches I've seen anywhere. Espadilla beach gets seriously crowded, especially on weekends, but the ones inside the park don't because they limit the number of visitors that are allowed to enter the park at any one time (so one should get there early if they come during a high season weekend).
However, given MRMIKE's comments in another thread, MA is one place he should visit but Samara might be the place he really needs to check out, as Pelo suggested. In the other thread Mike mentioned he was planning on touring CR with his wife with an eye towards finding a quiet spot on or near the beach to purchase and settle down. MA is certainly a great place to visit, which is why so MANY do (and why they have to severely restrict entry into the park), but I don't think it will serve his ultimate objective, which he didn't mention here. The MA area suffers from its on popularity with tourists. Outside the park is getting overdeveloped, putting huge strains on the environment and driving local prices very high. When I read he was looking to buy in someplace quiet, I changed my recommendation from MA or the northern beaches (Flamingo, Tamarindo), which are facing similar huge booms, to less visited Guanacaste beaches such as Nosara or Samara or even Dominical which is further south from MA.