We stayed at Rana for 2 nights early 2013 together with our 2 kids.
We agree with all positive comments given so far: comfort is indeed very basic (no electricity...), but obvioulsy this is not what you are looking for when coming to Rana.
I would insist on the fact that Don and Kheung obviously don't run their homestay to make money but to meet new people, share with them their knowledge of Cambodia and show the surrounding areas at any time of the day. This is very appreciable and rare.
The price they ask for this is a bargain.
Also Kheang is an outstanding cook!