I travel to Lanka regularly so am familiar with standards throughout the island. Usually stay at the Galle Face or Park Street on arrival. My partner and I had a week after travelling in India and booked the river house through the manager at park st. The same hotel group.
The trip from Colombo is straightforward, though the cut off to the hotel is a dirt track and our driver found it difficult to negotiate.
The villa is beautiful in structure and setting. Perfect position overlooking the Sri Lankan backwaters.
Ok some words of caution.
If you decide to eat here, (and it's difficult not to as it's isolated) note that there is no chef.
You have to pre order meals during the afternoon for dinner. I guess if you decide to take the family out early then you have to order lunch and dinner at breakfast.
Our first dinner was a disaster. Mine was cold and half cooked. I asked for the chef, and a guy in a tracksuit came out and offered to reheat my plate. Meanwhile my partners meal was cold but he didn't seem to understand the custom of eating together.
That was the 'chef'
First time I have remarked on this site

I stayed 2 nights here in January. I stayed in the Kirinda room which was absolutely gorgeous (although the small walled garden off the room wasn't somewhere I would have sat out in especially given the stunning river views from the main terrace).

The main wow factor for me was the river views. So peaceful sitting looking out across the gardens and river. The hotel can organise boat trips up the river on their own boat which definitely recommend although do take lots of change as you feel you are expected to leave donations at the temples you visit and buy cinnamon at cinnamon island - none of which I had an issue with but as I didn't have any small value notes on me it ended up quite expensive! The boat trip cost me 4500 (although I was told this was a special price for residents and the actual price should have been 6000) - I was travelling alone so not sure if this is a one off regardless of how many of you go

The staff were really polite, friendly and helpful and the food was amazing. You are given complimentary tea and biscuits on the terrace in the afternoon while you choose from that evenings menu which was a nice touch. The hotel also has wifi which worked out as about 80p for an hours access

Really enjoyed my stay and was a nice place to switch off and relax.

I found it quite hard to find the hotels website - the hotel is now owned by anilana and the river house can be found through their main website

This was our first stay in Sri Lanka and we shall never forget it. Everything was perfect: this exclusive place is in a beautiful spot, deep in the nature and very confidential (only 4 suites with stunning views, esp the master suite with its private pool on the upper terrace! A must);
The service is also perfect with great attention to everything without being "too much".
Last but not least, the food is absolutely fantastic. This is by far the best food we have tasted during our stay in Sri Lanka (and we have stayed in many different exclusive places! ). So if you wanna have an idyllic stay on your tour, book here without any doubts, you shall never forget it!
So

My boyfriend and I stayed at The River House in mid-November 2010 for 2 nights. We were hoping for a couple of days of pure relaxation in a beautiful setting and I'm pleased to write that's exactly what we got.
The hotel overlooks the river and this waterside setting was a nice change from the many beaches we'd visited - a great way to experience a different side of Sri Lanka.
We stayed in the Gin Suite which was enormous with a gorgeous bed, massive bathroom and outdoor jacuzzi. There is also a lovely communal pool.
During our time there we chilled out by the pool with books, wandered around the lush grounds and took a leisurely boat trip up the river where we saw loads of wildlife (monkeys, kingfishers, baby crocodiles) . The service we received was excellent and the food delicious. It was a nice treat having afternoon tea every afternoon with homemade biscuits/cakes!
In short, we would throughly recommend The River House to anyone visiting Sri Lanka.