Wow. For nine pages people have been talking about a user-removable battery, even though it clearly states in the news post that this was just a guess by a commenter at Engadget. Someone saw a pinhole and took a shot in the dark as to what it was for. I don't see Apple allowing users to replace their own battery.
Moving on from that, what's so hard to understand about a prototype enclosure? That should be pretty typical, right? All the pretty, visually-appealing aspects of the hardware probably get saved for the very end. You don't need a fancy unibody case to test a phone. This is probably a rough version that was made in-house (hence the seams) just for testing purposes. How old is that leaked image of the iPad with the iPhone sitting on top of it? You cannot assume that this prototype is recent just because the leaked pictures are new. If it's the same prototype that you see in the iPad picture, isn't it safe to assume that the prototype has been around for at least a few months? Apple could have changed a lot since then.
I think you'll eventually end up with a phone that resembles the iPad. I don't own one yet, but looking at pictures from Apple's site, iPad shows the same type of aluminum bezel around the edge of the device with the same speaker holes as this iPhone prototype. I'm sure the back will be a different material in order to allow for phone signal to pass through it. Otherwise, it just has a more square, industrial look which I think is nice.
I do think it's funny that everyone hated the plastic 3G case when its pictures leaked, but now people are upset that Apple may be taking it away.

I have a 3GS and I hate the plastic casing. I think it made the phone look and feel cheap. I would love to see them go back to something a bit more sleek and sturdy. If the new phone has a seamless bezel with a cool new glass or ceramic back, I'll be thrilled.