Getting there: We took the challenging path, through 7 miles or so of rough roads. It's doable with an SUV and I've seen a couple of normal cars attempt. What's challenging is not so much the steepness of the road but rather there are a lot of large rocks sticking out. I wouldn't attempt this road in a normal car, but I think technically it's probably doable. There's also a longer and easier path to get to the hotel (check the hotel website for directions.)
The river: We went to the park first. Yes, the river gets gray-ish during times of downpours, but we had mostly sunny skies. Although the hotel has a path that leads to the river, the park views of the river's waterfall and other volcanic features (keep walking past the waterfall) were far superior to the small piece of river you could see from the hotel path vantage point.
The grounds: The resort is lush and pretty, with flowers adorning tropical foliage. However, besides the path to the river (how many times would you really trek it?) and a swimming pool, I'm not sure what else there is to do there. I'm not faulting the hotel, but unless a tropical vegetation vacation is what you're looking for, I wouldn't stay for too long based on my personal preference. Having said that, the hotel is only a mile or so from the national park, so it's a great stopover after a long day of hiking.
The staff: The staff at this hotel exhibited some of the best customer service I have ever come across: polite, charming, intelligent. They answered all my questions, were extremely flexible, and one of them even sat with me for 20 minutes to suggest other places in Costa Rica I may want to visit. Truly incredible.