We absolutely loved Arenal Manoa! The hotel's property are all little bungalows spread out over a relatively large property. We got very lucky and our little bungalow was at the highest point of the hotel, with our windows overlooking the volcano. What a view! The room was very spacious, clean, and well decorated. I loved the "garden" in the bathroom, and it was very spacious as well. The AC worked great too. We actually enjoyed spending time on the little patio outside our room. We ate one lunch at the hotel restaurant and the food was good, if a little pricier than in town. Breakfast was good, and the views form the restaurant are gorgeous, with a big overlook of the volcano. The lush gardening of the resort is beautiful as well. We loved ending our day in the hot springs enjoying the happy hour drink special.
The one note I'll make is that while Manoa does have a hot spring, it is relatively small, so you will still want to visit one of the resorts that's got larger hot springs. That being said, I wouldn't think twice about staying here again. We are relatively frequent travelers and this is one of our favorite properties in a while.