Well worth a visit. It's just round the corner from the Royal Palace and the National Museum, so you'll be in the area anyway.
The one thing that hit me about Cambodia was the number of children begging on the street, selling souvenirs at tourist attractions, or simply working. I know the country's poor, but hearing about government corruption when families can't afford to send their kids to school is awful. That's why projects like this that promote education (in this case the rehabilitation of former child sex-workers) are incredibly important. That they fund it by selling nice food and souvenirs means there's no reason not to support it!
We ate in the cafe upstairs twice during our stay in PP, and the food was really good both times. The shop downstairs sells lots of nice jewellery, clothing and other bits and pieces, so good for souvenir shopping while supporting a good charity.