Angkor Wat was the cover feature of this past Sunday's New York Times travel section. There is absolutely no landmine risk in the typically touristed temple complexes at Siem Reap. Perhaps if you went ten years ago, but definitely not now. Angkor Wat is simply one of the most amazing places on earth, and hopefully that is why you want to visit Phnon Pehn in the first place. If it weren't for the country's sad recent history, Angkor Wat would probably be the premier destination in SE Asia. I spent four days there and two in Phnom Pehn in 1998.

Unlike Siem Reap, Phnom Pehn can be dangerous at night and has every bit the feel of a "Wild West" town (in a nice development economics kind of way). This was true two years ago and I don't think much has changed, with the exception of easier internet access perhaps. Phnom Pehn was one of the few places in the world where I felt uncomfortable walking outside at night (you will be told this by every budget/independent traveler you will meet), which is a shame because Cambodians are very friendly. It used to be that even locals didn't venture outside at night, but when I was there that was changing and you would notice families spending the evening in front of their homes drinking tea and gossiping with neighbors.

If you stick to main tourist destinations (the above posters made good recommendations -- I would also add the kitschy Russian Market as a nice place to pick up souvenirs), Phnom Pehn is fine. However, if you decide to "go out" at night, you will discover an abundance of arms. Every bar/nightclub has at least one bouncer with a handgun. He iss invariably backed up by two other guys with ready access to unconcealed AK-47s. If you do go out at night, you will also discover that prostitution is rampant in the city. Almost overnight, Cambodia sadly now has one of the highest AIDS rates in Asia.