WikiLeaks just released hundreds of cables from the US Embassy in Phnom Penh, some dating back to the early 90s but most post-2005. The cables can be viewed here:
WikiLeaks leaks: US Embassy, Phnom Penh, Cambodia cables, released by WikiLeaks July 2011
After a quick browse through, the US looks pretty good throughout the cables. I haven't found any big gotchas yet. Fairly normal embassy correspondence. Perhaps a little embarrassing at times to have all of one's private conversations, musings and opinions publicized unfiltered, as it would be for anybody, but nothing untoward (at least for the US) that I can find yet. Generally good political analysis, mostly accurate or at least one can understand how a reasonable person could arrive at that conclusion. Not that different than one might read in the local English language press, but deeper and more informed, as well as a bit more open and incautious as the writers thought they were engaged in private, non-binding conversations. Where specific interests are pushed by the embassy, the US seems mostly a force for Good (anti-sex trafficking, anti-drug trafficking, pro-democracy/human rights/political freedom), if not sometimes rather pragmatic in its interests.
Unfortunately WikiLeaks has once again failed to delete the names of some private individuals, including asylum seekers and those who provided information to the embassy. Potentially dangerous for the individuals named, who now may become targets for persecution. They can thank Assange for hanging them out to dry like that.