We were very happy with our stay in Campo Verde (three nights, late April 2013).
The cabins are spacious, clean, with high ceilings and big windows. There's a safe and a mini fridge. All cabins have private terrace with nice comfortable chairs for taking in the view. All cabins have a great view of the volcano - don't fuss too much about which cabins you get.
The breakfast was simple and tasty. The staff were at all times friendly and helpful - I did find them a bit lacking in terms of recommendations of which activities were best, though that may be because there's a huge amount of different fun things to do in Arenal area. Generally though the lady at the desk was always really helpful, ringing around for me, speaking to car hire company everything.
Campo Verde is about 9km outside La Fortuna. We hired a car for one of our three days so we could drive to Arenal Volcano National Park. The other days we used taxis to get into town - it's about $15 each way in a taxi in to La Fortuna.
I would happily recommend this place or come to stay here again. Great value, and really nice clean spacious rooms.