If you are entertaining the idea of visiting Wachau Valley, staying in Durnstein is a good idea as it is fairly centrally located. More importantly, it doesn't get any more charming than this.
We loved the setting of Hotel Richard Lowenstein. Picture perfect, just like what you hope you will experience when visiting a charming small Central European town. The hotel, its restaurants, terrace and English garden are overlooking the Danube river; the garden and its pool area are set against old city walls. The facilities had a calming, tranquil atmosphere overall. It is also a great place to stay if you are cycling through the area (there was a Backroads tour crew and guests at this hotel).
Breakfast was included and it was fabulous.
One of the evenings we stayed there was chilly, and the lobby had a roaring fire going in its fireplace, with cozy chairs and tables around it and people hanging out.
I think the rooms could use more comfort. Most hotels in Central Europe are spartan in terms of decor and comforts, but for a place like this I would have expected at least a pillow that supports my neck. In fact, lots more pillows. The bathrooms work, but are tacky and very cheaply put together. Mattresses are not great. Don't expect lavish room furnishings. But then, you won't be spending much time inside.
All in all, I would stay at the same place again.