Good choice! I have stayed at this hotel a few times and can only confirm what you describe. The beds are super comfortable and the staff is very hospitable (on every level... haha). It is indeed a place where you can easily relax by the pool all day. Nude swimming is even allowed there if you wish.
If you ever go back, I can recommend taking a tour to the Tuol Sleng Genocide Museum (in old prison) and the Killing Fields. You can also book this via the hotel by Tuk-Tuk. Not exactly a fun outing, but a must-do because of how impressive it is and the stories you hear there about the history of the country.
I really don't understand how you can say that about the breakfast at Arthur & Paul. How much do you want to eat for breakfast, for heaven's sake? You get a fresh croissant, a chocolate roll, another roll, an egg of your choice (like the famous Egg Benedict), various toppings, yogurt, tea or coffee, juice... More than enough!