they may share a border, but cambodia and vietnam are worlds apart.
as soon as we crossed the border (by boat) you could see interesting temples on the banks of the river with architectures unlike anything in vietnam. in phnom penh the temples, museum, and monuments have pointy spires, nagas (large snakes with 9 heads), apsaras (dancing nymphs), and other mythical creatures that we never saw in vietnam. the architecture here seems much closer to thailand than to vietnam.
the food is also much closer to thai food than vietnamese food. i've had lots of soups (sometimes made with coconut milk and spices) and curries here that remind me of thai food and have no connection with vietnam. we've stepped into a compleatly different culinary universe.
when you walk around phnom penh it has a very different feel from any city in vietnam. the streets are not as crowded with vendors and many shop fronts are permanently closed. (presumably from the lack luster economic situation?) walking around phnom penh you see that many of the streets in the city center aren't even paved and are simply very bumpy dirt roads.
the road situation in cambodia is much worse than in vietnam. cambodia supposedly has one of the worst road systems in all of asia. this becomes immediatly apparent when you take a taxi almost anywhere. (for example, going to the killing fields or any of the temples outside of siem reap.) most times you are driving very slowly and weaving all over the road trying to find the best path to avoid the REALLY big holes in the dirt.
there are also much fewer motos, but many many more cars, trucks, and SUVs here. for cars you see toyota, honda, lexsus, infinity, and mercedes. for SUVs and trucks you see the same brands as well as subaru and ford. some of these vehicles belong to NGOs, but not as many as you'd think. to me this seems indicative of a much smaller middle class in cambodia. the gap here between those who can't afford a moto and those who can afford an SUV is much greater here than in vietnam. right now in cambodia corruption in the government and misuse of internation aid and money brought in by NGOs is apparently pretty rampant. (hell, i even saw a toyota with chrome spinner hub caps in phnom penh... truly amazing.) in siem reap there was a bookstore where the owner had a Harly Davidson motorcycle, a really big hog, at least 1000cc. in vietnam, it's not legal for anyone other than the police to have a bike bigger than 150cc.
the poverty situation here also seems much worse than in vietnam. there are many more beggers on the streets (both in phnom penh and siem reap.) children following you for a couple blocks with their hands out either mumbling incoherently or saying "money, money" over and over again. children and mothers carrying babies are asking you for money. old toothless and cripple people are asking you for money. people with their legs and arms missing loaded onto carts are asking you for money while their friends push their carts along side you while walking down the street. when ronda handed a half empty plastic bottle of water to one begging girl, another begging boy standing next to her immediatly knocked her down and took the bottle. when i got off the boat in siem reap i was immediately swarmed by children all asking me for the pen that was clipped to the outside of my backpack. there really wasn't much of this in vietnam and here it's pretty continuous and very much in your face.
there are a some exceptions though. most of the rampant begging occurs in the tourist areas. when you leave the center of town (in siem reap) you don't see as much of it. also, the authorities seem to put a stop to it in certain areas of phnom penh. in phnom penh we stayed in a hotel on the river front and at night we pretty much only walked up and down the waterfront to resturants and bars there. (cambodia is a well armed country and armed robbery is not uncommon here, so we were playing it safe.) all along this strip there were multiple police officers on every block and the only people who would hassle you were tuk-tuk drivers who would ask once if you wanted a ride and if you said no they would back off.
another issue when traveling here is the pollution. in phnom penh itself the situation wasn't too bad, but once you get outside of town the amount of dust and dirt in the air is very high. while in siem reap the amout of dust and exhaust in the air left me and ronda with soar throats and stuffed irritated noses for the extent of our stay.
in general, people here seemed more congenial that in vietnam. social and financial interactions seemed to go easier and people seemed more strait forward and honest. initial prices for things seemed more resonable and the haggling process was much easier here than in vietnam. (on many occasions in vietnam people would try to sell us things at extravagent prices and then be compleatly unwilling to bargin, even if i knew what the price should be and was willing to offer them something reasonable. that never happened here.) with one exception, tuk-tuk drivers seemed less pushy and persistant that moto drivers in vietnam.
in all, i really liked it here and i wish that i'd had more time to explore some more. some other interesting areas to see around the country would be battambang, the coastal areas, and the nothern mekong delta region.