We had a wonderful stay at Casa Santa Maria. Jim, the owner was so informative, answered every question within minutes over email and text and could not have been more helpful. Just like the other reviews say, the road to the house is a bit rough, but you are staying in the jungle and well worth it to get away from the city. It was a rocky road for about 30 minutes, you should likely have a 4x4. Once we got the house we had a warm welcome from Lucy, who cooked and took care of the place. The food was excellent and the sounds from the jungle were really neat. We had the entire house and it was beautiful, quiet and peaceful. There is no television and the internet is pretty limited, so I recommend downloading anything you need before leaving. Only thing I thought that was lacking was a central area to hang out with a couch or chairs downstairs. We were so busy during the day that by the time we got back we were exhausted. We ate dinner, relaxed and would fall asleep by 8 or 9 pm!
The pontoon boat tour with Lucy's family, Laz and Millie (spelling?) was excellent and well worth it - a local jungle tour with waterfalls, relaxation and a little hiking just down the street from the house ( 5 minutes drive). I definitely recommend this. We also did the ATM caves and Tikal, both long days and a bit of a drive from the house, but totally reasonable day trips.
Overall, a highly recommended place to stay.