Anyone who hasn't visited Cambodia (or SE Asia in general) should go. At least once in your life. It's cheap, the people are kind (do not insult the king of Thailand though) and the incredible diversity of people streaming in from India, China, and later France has left behind an amazing cultural chronicle. Cambodia will, for better or worse, forcibly remind you of both the heights (Angkor) and the depths (the Khmer Rouge) of humanity.
Note that the KR almost certainly would not have come to power and killed 1/3rd of the population if we hadn't bombed the shit out of eastern Cambodia during the Vietnam war. (Henry Kissinger received the Nobel peace prize for these antics) Almost exactly like Isis, except the KR didn't see the point of destroying their own heritage. So in spite of the odd bullet hole, Angkor and surrounding sites are as awesome as they were when Mouhot stumbled upon them in ~1855. (The Frenchman could not believe that "savages" built such incredible temples and attributed them to the Romans.)
Amazingly resilient people with a glorious legacy that continues to grow as we learn more about it.