How can I display a splash screen for a longer period of time than the default time on an iPhone?
I agree it can make sense to have a splash screen when an app starts - especially if it needs to get some data from a web site first.
As far as following Apple HIG - take a look at the (MobileMe) iDisk app; until you register your member details the app shows a typical uitableview Default.png before very quickly showing a fullscreen view.