For my iPad scheduler app I want to follow the overall settings for 24 hour time. Guess what? You can't set that on the simulator! Under Settings -> General they flat out skipped the Date & TIme options. Why? There is no reason to not have this setting available. I have to do all my testing of time and date formatting on the device itself.
I am trying to be as friendly a developer as possible. If you like 24 hour format then times should appear that way in all your apps. I am used to AM / PM so I generally use that format but Kevin != rest of world.
At least I am not doing a ton of time and date formatting meaning it was pretty easy to test on the device but I should not need to switch to that to test an OS related feature.