From the transcript:
OBAMA: It is more difficult than I think a lot of people realize and we are going to get it done but part of the challenge that you have is that you have a bunch of folks that have been detained, many of whom who may be very dangerous who have not been put on trial or have not gone through some adjudication. And some of the evidence against them may be tainted even though it's true. And so how to balance creating a process that adheres to rule of law, habeas corpus, basic principles of Anglo American legal system, by doing it in a way that doesn't result in releasing people who are intent on blowing us up. [emphasis mine]Note THAT construct: "It is more difficult than people realize." It was more difficult than candidate Obama thought during the campaign. President Bush and Vice President Cheney knew EXACTLY how difficult it was. In fact, it appears they had it about right.
Apology implied and accepted.
The discussion about Guantánamo continued:
STEPHANOPOULOS: So not necessarily first 100 days.
OBAMA: That's a challenge. I think it's going to take some time … I don't want to be ambiguous about this. We are going to close Guantánamo and we are going to make sure that the procedures we set up are ones that abide by our constitution.
See what I mean? Closing Guantánamo immediately is an easy campaign pledge. Closing it "some time" is the difficult reality of serving.
There is a world of difference.