I have created an application that receives BOOT_COMPLETED within a receiver using the following filter:
Some devices after Android 3.1 will not give the app control after the BOOT_COMPLETED receiver.
Google has long said that users should launch an activity from the launcher first, before that application can go do much. Preventing BOOT_COMPLETED from being delivered until the first activity is launched is a logical extension of the same argument.
I do not know which devices it makes a difference on though.