I'm quite surprised by the lackluster reviews of the iPhone 5 so far. My take is that most of these folks are disappointed that there is no peak higher than Mt. Everest. Worse, Apple was very leaky this time around, so by the day of the announcement most of the facts were known.
There could be other things in play. Android phones, as a group, outsell iPhones. Windows 8 phone is just around the corner and the pundits like what they see (and they haven't seen much). If you're in the business of prognosticating and putting stakes in the ground, it's bad if you go all in for the iPhone 5 just to find out that the Nokia Lumia 920 is an iPhone-killer.
My little contribution is brief. I think there are two important issues here - brand loyalty and physical phone size.
Apple brand loyalty is phenomenal, in my experience unprecedented. I have yet to meet someone who doesn't love their iPhone and I have yet to meet someone who has switched from iPhone to, say, Android. (There must be some.) This alone means that as long as Apple can make reasonable updates to the phone with reasonable frequency, it will likely be able to sell into its existing market easily. So far Apple has been uncanny in its ability to deliver feature and function with great market timing and unless that ability was vested solely in Steve Jobs (which I doubt), I expect it to continue for some time. Apple can continue to draw new customers, although brand alone can't grow Apple's share by much.
One common criticism of the iPhone 5 is its size. Reviewers compare it to other phones, such as the Samsung Galaxy S3, and deem the iPhone too small. Apple, probably anticipating this, included a pointed reference to the width of the iPhone 5 being the same as the iPhone 4s and explained that this was done to assure one-handed (one-thumbed) operation. I think there is more to this than meets the eye.
Apple is generally not on the defensive. The only significant exception to that rule was iPhone 4 "Antenna-Gate" when Jobs was clearly unhappy to be making the carefully crafted presentation in which he was forced to refer to other products. This means Apple is unlikely to hop on stage and announce that the Galaxy S3 is too big.
But it is. For a phone, that is.
I think Apple is absolutely right to attempt to constrain the size of the phone. I realize that these phones are, in fact, tiny tablets that happen to have a radio and a phone app and that many, many people rely on the application functionality of these devices in their daily lives. The computer aspect of the device transcends the phone. We have decades of experience that tell us that users want more screen real estate and will generally only trade it away for specific functionality or mobility.
As I've written before, I plan to buy a Windows 8 phone. I was impressed by the form factor of the Samsung Focus 2, which is very close to the iPhone 5 and almost exactly the the same size as the new HTC 8s. But the new Samsung ATIV S Windows 8 phone is as big as the Galaxy S3, which means big. Too big. The Lumia 920 is big. So far, only the HTC 8s is sized to my taste. Too bad it's light in other technical respects, but it is small enough.
So if I think the larger phone sizes are too big, what about the phone as computing platform? I know this may sound strange, but this is where I think we get into two-device territory. I can't tell you how many iPhone owners I've seen who also carry an iPad, especially mobile business people. These are folks who used to carry a phone and a laptop and have downsized by buying a tablet. And that is why I think Apple decided to create a smaller iPad - to capture more of that market. In that context, keeping the size of the iPhone in check makes perfect sense.
I wish the Windows phones could be as small as an iPhone without sacrificing performance but I doubt it will happen soon. Apple, knowing it can sell millions in the first few days and having only one model with one form-factor, can afford to engineer that one model to the nth degree. That's why the iPhone display can come closer to the edges of the device than the Windows phones do. With the smaller Windows market (for now) and multiple manufacturers, it is more difficult to achieve the economies of scale required for that level of engineering.
At any rate, I think the iPhone 5 meets requirements in both brand loyalty and size. It is thus a worthy successor to the 4/4S and will do well in the market it created.
Those who think otherwise may be one phone generation early. But I wouldn't bet on it.