Seven years after its initial release, Apple’s iPhone is still the next big thing, a sensation that continues to excite, and the single most important reason that Apple Inc. is the most valuable company in the world today.

Apple just released the latest versions, the iPhone 6 and iPhone 6 Plus, on September 19. I think they’re a mistake. A lot of other people feel differently, with huge numbers jumping on the bandwagon and buying them.

The iPhone 6 and 6 Plus, along with Apple’s mobile operating system, iOS 8, which was simultaneously upgraded, have had their problems. At least at this early point in their release, this has caused Apple’s astronomic stock price to take a small but appreciable hit.

The biggest difference between the iPhone 6 and 6 Plus and their immediate predecessors, the iPhone 5, 5C, and 5S, is that they’re bigger. With the iPhone 6 the screen size jumped from 4.0 inches to 4.7 inches, and with the iPhone 6 Plus it jumped to 5.5 inches.

This puts them more in line with the sizes of the iPhone’s most immediate competition, the smartphones of Samsung. But it also makes them difficult, and sometimes impossible, to fit into your shirt pocket. This, to me, is their main problem.

For other people, who keep their phone in their pants pocket or purse, this may not be a problem, and they appreciate the larger size. It makes video on the phone more compelling, it makes text easier to read, and it makes an already easy-to-use phone easier to use.

But pants-pocket use has led to another problem, this one unexpected: the bending of the phone out of shape caused by the bending of your leg while sitting and standing, particularly when wearing skinny jeans. The iPhone 6 and 6 Plus’ superthin all-aluminum design hasn’t led to widespread reports of breakage, just the development of annoying bends or kinks.

The iPhone 6s have had other problems too. They’re supposed to have longer battery life than their predecessors, but some people have experienced a shorter battery life, preventing them from using the phone all day without recharging.

The main problem with iOS 8 has been sluggish WiFi, particularly with version 8.0.1. Short battery life, lost cell service, crashing apps, and botched fingerprint reading are other issues.

Users of the iPhone 4S and 5, 5C, and 5S can download iOS 8 as a free upgrade, though not users of the iPhone 4 and earlier models, which are incompatible with it. Some iPhone 4S users upgrading to iOS 8, however, report serious slowdown and other problems. iOS 8 is also available to users of the iPad 2 and later and the fifth-generation iPod Touch.

Apple continues to release bug fixes, or updates, to this upgrade, and if history repeats, which it should, these problems will clear up in the future. But it gives added weight to the old advice to wait a bit after the release of an update or new program for problems to be fixed that weren’t identified in the testing phase.

Fortunately, among the many new or improved features of iOS 8 is Battery Usage, which identifies apps that may be hogging battery power, giving you the option of deleting them or modifying their use. Launch the Settings app then select General, Usage, and Battery Usage.

Among the other improvements that I’ve found the most useful are how the Siri voice recognition feature now displays text as you speak it and how the Calendar scheduling program shows all of your upcoming events.

On the hardware side, among the other improvements with the iPhone 6s is the built-in camera. It still uses an eight-megapixel sensor and five-element lens, but focus speed is a lot faster, a timer is now included, and video capture is improved.

The camera of the iPhone 6 Plus, which features optical image stabilization, is supposed to be even better than that of the iPhone 6, but reports indicate this doesn’t lead to a big real-world difference in image quality.

Because of their popularity, iPhones remain pricey, even refurbished older phones. With a cell contract, the iPhone 6 starts at $199 for a unit with 16 gigabytes of storage, while the iPhone 6 Plus starts at $299 with the same storage, which is adequate for most users. Without a contract, the iPhone 6 starts at $649, the iPhone 6 Plus at $749.

A look around the web indicates that a refurbished unlocked Apple iPhone 5 would set you back more than $400.