I have mixed feelings about Wikileaks. On the one hand, I think abuses, crimes, and the like should be exposed in general. I do feel Wikileaks made a large blunder by releasing names that could put peoples' lives in danger in some of their releases, but it appears they're no longer making that mistake at least.
On the other hand, I think one must always consider the potential harm every leak could cause. For example, if you had a video of General McChrystal burning a Koran and laughing about it, you probably shouldn't make it public. Send a copy to some higher ups in the US government and make sure they know they should get a leash on him before he does cause an incident, sure, but releasing it will just stir up hatred and could lead to many deaths.
This is why I'm much more skeptical of the benefit of the more recent diplomatic leaks than I am of the Iraq/Aghanistan ones. Much of the information that was released revealed nothing criminal or even unethical but could still lead to international incidents. I believe secrecy does have it's use in diplomacy much as it does for individuals. Being able to frankly discuss opinions of foreign dignitaries without fear of word getting back to them could very well aid in the establishment of good diplomatic relationships with other countries.
Besides, while some people may hope for complete transparency in government, I don't think Wikileaks will lead to that in the long run. I suspect it will just mean billions upon billions being spent beefing up security and coming up with procedures making it easier to discover who it was who was behind a leak. If they stuck to releasing only actual crimes and abuses, it would be harder to justify such expenditures without looking like they have something to hide.