If Apple would have done this, I (and I would think most people) would be fine with it. I don't have a problem with Apple saying they don't want to give the Gov't the ability to get in to any iPhone they get their hands on, but when they have a device that could clearly have ties to national security, i.e. terrorists' phone, then there's no reason why they shouldn't be willing/able to do that.
But, I saw reported yesterday that the FBI has been trying to get Apple to unlock several other phones for over a year, but those others were filed in private, so no one publicly knew about it. Now the FBI has deliberated blown this particular case up in the media, trying to use it as leverage to get the secret sauce to unlock all the other phones too. Of course, the public mostly think it's a good idea because it's a terrorist IN THIS CASE, but then as MA pointed out, you unlock this one and Pandora's box has been opened.
I think it's shameful the gov't is trying to exploit this situation for their own benefit.