The compulsion of Apple is I think what bothers me most. To use the often abused and not quite accurate safe metaphor, If I have a safe, and the FBI has a warrant for it, they can go in it. I don't have to unlock it for them. I can make them break in (They won't buy me a new safe, that's on me).
So they got a warrant for the phone. Cool. There's the phone, have at it. If the guy were still alive I imagine he'd be sitting back laughing at them before he gave up the code. Good luck.
So the FBI has a warrant for something they want, but can't get. So they asked Apple for help. I'm OK so far. Apple thought it over, and declined to help. That's their business. Apple is not a party to the criminal prosecution in any way. I don't see how there's any way to compel them to do anything they don't want to do. (That's an oversimplification, I know the law the .gov is using, I just think it's stupid, and not as applicable as judges seem to). Just like in my safe, they could ASK a locksmith to open it for them, but they shouldn't be able to COMPEL the locksmith to open the safe.
Now I know that data encryption is a little more complicated then just a safe with papers in it, and that's why the gov is so cranky about it, I just don't really care. If they can crack it, or hire someone freely to crack it for them, hey cool, good luck. But you don't get to just make someone break in for you.