My phone is covered with overlapping, often smeared, fingerprints. I'm sure than an expert could isolate a good copy, but it wouldn't be a trivial task.

I'd certainly like some more security on my iPhone, but not so much that I'm willing to type in a code every time I pull it out. I'll certainly use the fingerprint sensor.

Yes, I currently don't use a passcode at all, because it is too inconvenient. So I'm not particularly concerned with whether the fingerprint sensor can be broken by somebody who has managed to get hold of my fingerprint and go through the rather elaborate process described--it's still going to be better than no security at all.

But has he previously trained it to recognize his middle finger?

Samsung is also moving to 64 bit on their phones.

So do you really believe that both companies are going to all of this effort and expense is just for the sake of marketing hype, or is it just possible that the two companies with the most experience with smartphone development know more than you do about the advantages of 64 bit architecture for this type of device?

Nobody did market "cores", as in a small number of parts of a GPU.
Here's one example
Here's another.
Here's another
Sure seem to be a lot of nobody's around.

What about a fallacy. Just because they doubled the performance doesn't mean that it's because of 64 bit. It's more likely a better architecture and increased clock speed.

It's more likely the whole combination of features. Apple has gotten very good at optimizing performance for mobile devices by cleverly matching the capabilities of their chips to their software. I doubt if going to 64 bit is solely responsible for the increased performance, but I also doubt if it's irrelevant. A doubling of effective performance is a big change for going from one generation to the next of a chip. Apple certainly didn't double clock speed--that would be too expensive in terms of battery usage.

I think that the notion that 64-bit offers little per formance improvement aside from a larger address space comes from people who are more familiar with PCs, which have loads of RAM to play with. But RAM is power-hungry, so cell phones are RAM-constrained. As a result, cell phones are constantly shuffling data back and forth between RAM and Flash memory, and it needs to do this very fast, because users are impatient with lag in a mobile device. And moving data is one place where wider registers yields a big benefit.

Yes, we all know that Apple, like other for-profit companies, is in business to make money. Different companies have different strategies to do that. Apple clearly believes that making premium-quality products will bring them more money. So far, it's been working.

If you've never heard anybody touting the number of cores in their GPU, you haven't been paying attention to marketing of graphics cards. Because graphics calculations are highly parallelizable, and because the parallelizing can be handled by the OS, without requiring extra effort from app developers, GPU performance particularly benefits from a multi-core architecture.

Apple's phones have always exhibited performance that is competitive or better at the time of introduction, and the user experience is always very snappy, with lag nearly absent. Historically, Apple's reports of speed increase over previous generations have proved pretty accurate when people got around to benchmarking them, so it is likely that will prove true once again. A doubling of speed is a quite respectable performance increase over a year. So maybe Apple was not mistaken in thinking that the 64 bit architecture offers real advantages given the design of their phones and iOS. But it required substantial extra investment on Apple's part, because Apple's developer package had to be revised to create 64 bit apps, so that app developers would be able rapidly update their apps to take advantage of the new architecture. If Apple just wanted bragging rights, more processor cores would have been much cheaper.

You miss the point. This is not for people who are "security conscious." No matter how reliable and secure the fingerprint sensor turns out to be, it is axiomatic that adding a second way of unlocking your phone in addition to the PIN cannot possibly make it more secure than PIN alone. And who is going to trust the fingerprint method without a PIN?

This is for the people who currently aren't using a PIN at all, because it's too inconvenient.

With Apple's buying power, they could have any cpu they wanted. If they've chosen this one, it's because they think it has distinct performance advantages for the way their products are used. If anything, Apple has avoided playing the features game, sticking with a dual-core architecture rather than the sexy-sounding quad core. And the general experience of Apple devices is that they are very snappy.

It's pretty unlikely that Apple would go to the expense of transitioning to a 64 bit architecture unless it gave them a meaningful performance benefit. Smartphones have relatively small RAM, yet they are expected to respond to user commands nearly instantaneously. It is clear that iOS devices are constantly moving data around to economize on memory space. And moving data around certainly benefits from wider registers.

A 64 bit processor processes information in larger "chunks," which speeds things up. So this is probably a big part of the rather dramatic claimed increase in speed.

If you are like most people, you trust your trash pickup service with your fingerprints (and all of them, not just one) every week. Not to mention the waiter at every restaurant you visit.

So in an occasional rare situation, you have to enter the unlock code. Still a lot more convenient than having to enter the code every time. I don't use an unlock code because it's too much of a pain, but I'll use this.

May be a battery life issue. Unlike some of its competitors, Apple has historically been very reluctant to compromise battery life, and if it's a choice between more power and more memory, they'll go for more power.

Actually, the screen is larger than on the iPhone 4, although as is expected with the alternate-year "s" models, it is the same size as on the iPhone 5.