I feel sorry for Obama having to deal with such a difficult issue. He is in a position where the right thing to do is very dangerous and in some aspects counter productive. However I believe firmly that there should be a full scale investigation.
The alarming thing is not that people were tortured. The alarming thing is the sophisticated network of people conspiring to undermine the law. Torture is not the only example of the Bush administration finding ways to undermine the law. What has happened is that our nations most powerful criminals have succeeded in manipulating our legal system. It is a good thing that they only had eight years because the legal grounds that hold our Nation together had been eroding underneath us.
Obama's task is to dismantle the conspiracy to undermine the law. The thing that makes this hard is that its part of the CIA's job to undermine Law. One of the main reason the CIA is so secretive is that many of it's operations are illegal.
So the main issue here is if and where we draw a line? The CIA has gotten away with worse than torturing suspected terrorists. Does anyone remember the mind control experiments ran by the CIA in Canada. Which were carried out on American and Canadian patients. These people were strapped to beds, kept sedated for months on end with head phones strapped to their heads playing voices and noises, they were exposed to shock therapyat 30 to 40 time the power, with a goal of wiping out memory. The victims of this experiment essentially forgot who they were, many of them thought that their "doctors" were their parents.
http://en.wikipedia.org/wiki/Donald_Ewen_Cameron
To my knowledge, nobody was prosecuted for this abuse of our own people. If I am not mistaken, that was illegal. My point here is that the CIA has a history of abuse of power and disregard for human rights. Of coarse we like to hope that the atrocities of the 50's 60's and 70's were isolated events and that things have changed since then, but under George bushes watch, there was a fear that dark sides and secrets within our government were coming back and trying to gain a foothold. This is what needs to be protected against, and I think it is worth the effort.
However there is also the argument that we need a body within our government which can carry out our dirty work illegal or not so long as it keeps America Safe. The problem is how can we trust this body with so much power and secrecy, especially given the history?
Now Obama probably wants to draw some kind of line to the extent that the CIA can go with regards to illegal and perhaps disturbing activity regardless of so called security reasons. Releasing the memos acts as some kind of middle ground in line drawing with a hope of not making enemies with the CIA, and with hopes of getting re-elected. So this is a huge challenge, and there is no perfect solution, but I think he is doing the right thing.
I think that if Obama wants to be successful, he needs to slowly implement a body of strong oversight that infiltrates deeply into the realms of our secretive organizations. This will provide protection against potential threats from the inside because if something is overboard or entirely out of line, it can be released and people held accountable. So it is kind of like a warning, you won't be punished this time, but if you cross us, then you will be front page news.