One of my absolute favorite iOS features in iOS5 before I switched to Android was the new "take a photo from the lock screen" button. I felt understood when they added that.
It's something they borrowed from Windows Phone 7, which has allowed you instant access to the camera (albeit via a mandated hardware button) while the phone is locked.
Is it just me that press the home button three times everytime I want the camera icon to appear? The first press is because that's how I do it all the time and then I remind myself that it actually takes two presses to make the icon appear. By the time I actually manage to make the camera appear whatever I wanted to shoot is usually gone. I really want an hardware camera button like on Lumia.
That's one of the things I loved about my N900 when I first got it. When you slide open the shutter, you're instantly in camera mode. No waiting, no unlocking.