Don't take our word for it, listen to the people at Rough Guides. They held an online poll "What is the friendliest country in the world?" and Cambodia was by far the top answer, and a popular choice among staff members and rough guides twitter followers alike.
Livability surveys (e.g. by The Economist) regularly put Phnom Penh in the bottom 10 of "Livable Cities". Well, I say this: these survey guys are sitting overseas just collecting data, but have never actually been here, let alone live. This is for them: