I'm NOT comparing the N900 with the current or future iPhone here, I'm congratulating Apple on designing a tiny logic board.

If you want to discuss the N900 feature set in terms of the iPhone then within the context of this thread, any additional components or features present in the N900 - such as those you have mentioned - can be added to any logic board at no real cost in terms of size.

Keyboard? Just a few wire connectors. SD socket? Another few connectors. These connectors may be missing from the new Apple logic board but adding them wouldn't be hard or increase it's size by much, if at all. Adding the keyboard itself and SD socket to the *device* would increase it's overall bulk, but that's not the point of this thread, which is about the remarkably small Apple logic board.

As for a replaceable battery - it's something that matters to some consumers, but has nothing to do with the logic board design.