I haven't given the new iPhone 6 a whole lot of thought, to be honest. I have an iPhone 5C, and feel it's fast enough, and does all I want it to. At the end of the day, an iPhone is not a computer, and it should not be just about how fast it moves. Are there bugs? Is it really that much of an upgrade?
It's debatable whether or not the A7 processor in the iPhone 5S was fully exploited, as there are few apps that really put it to the test. With that in mind, the A8 processor in the iPhone 6 doesn't seem to be a compelling reason to upgrade. Perhaps that will change as new, more demanding apps are released, but for now, the benefit seems relatively minor.
The new A8 processor is great- it's faster than any other processor previously placed in an Apple phone. But how fast do consumers really need? Plenty of prospective phone purchasers are content with the speed of previous iPhones, such as the iPhone 4S and the iPhone 5. Given the cost of the iPhone 6, one would be money ahead to simply purchase an iPhone 5. The A8 processor is a luxury that many people cannot afford in these tough times.
I feel that to purchase each new generation of iPhone is merely playing into Apple's plans of taking as much money from consumers as possible. Each model is slightly different than the last (often requiring new accessories) and it is generally not worth the upgrade until two or three models have passed. Today's culture of "buy now, throw away tomorrow" is wasteful and bad for the environment and the consumer's wallet.