They specifically recommend against using your logo as a splash page, but most people do it anyway.
For more complex apps, especially apps that maintain state, this becomes impossible. You can make your splash image your "home" view controller, but if the app is launched from a URL (a large use case for many apps) the user will see an "empty UI" that is not what they're looking for, suddenly replaced by UI they are looking for.
Making matters a bit worse is that, at least up until iOS6, switching between apps (not just a cold launch) can also show the splash image briefly - but your app snapshot remains in memory, so you cannot guarantee the "empty UI" is what your user actually ends up looking at.
Splash images suck, but for a lot of apps they are the least of several evils.
It feels like Apple is advocating using a really ugly hack to make it look like app loading times are shorter than they really are.
"Avoid using your launch image as an opportunity to provide:
- An “app entry experience,” such as a splash screen - An About window - Branding elements, unless they are a static part of your app’s first screen
Because users are likely to switch among apps frequently, you should make every effort to cut launch time to a minimum, and you should design a launch image that downplays the experience rather than drawing attention to it.
Generally, design a launch image that is identical to the first screen of the app."
If you do this, as an iOS developer, you should have your developer program revoked...