Is Wikileaks an embarrassment for the U.S. government and nothing more? Well...
Look at this article, for example. It uncritically lists two of the things we've learned from the Wikileaks release of diplomatic cables as "North Korea supplied Iran with long-range missiles" and "Iran used the auspices of the Red Crescent to smuggle spies and weapons into war zones." True, the text of the article uses more accurate "the U.S. government believes that" language. But that subtlety appears to have slipped the minds of many of the commenters, who are now musing that here is new information that they didn't know.
If only Wikileaks had been around before the Iraq War. Then it could have been leaked that the U.S. government believed that Iraq was stockpiling biological weapons, and funding the 9/11 terrorists. And it would have been a leak, something that they didn't want people to know -- so of course it's correct, right?
Lest people think that I'm positing some conspiracy theory, I'm not. But diplomats and other spies routinely write back things that they confidently believe that are in fact not true. Diplomats and other spies who want to rise through the ranks also develop a talent for writing back things that they know that the politicians in charge want to hear. These leaks are pretty much worthless from the point of view of determining whether the events in question actually took place.