I'm all for transparency in government, but what Assange is doing isn't much more than embarrassing to the US. None of the leaks are really all that surprising or earth-shattering, they're just confirmation of policies and opinions that are already pretty much common knowledge. It's surprising to me that he'd risk his safety and freedom over what is, relatively speaking, pretty insignificant stuff.
It's also not surprising in the least that the rape charges against him were reinstated after the recent leak, when they had previously been dropped. The US and other governments affected are going to want to get at him any way they can. He should count himself lucky that they're trying "legal" means (I use the word loosely, since the reinstatement of the charges is flimsy at best) rather than finding he's been whisked away to a secret prison somewhere to rot for all eternity without a trial.
As for the man himself, based on the interviews I've seen of him I find him to be kind of a smug douche, which is a shame. And his motives seem far from pure to me. There's no honor in stirring up trouble for the sake of it, that's just so much anarchist bullshit. I'd be much more inclined to side with Wikileaks if it were headed by a decent man who was actually doing some good, but as it is Assange is just making already tense foreign relations worse.
And anyone who thinks this will help bring about more government transparency and accountability is fooling themselves. It's going to do just the opposite.