There were reports that Apple had stopped taking pre-orders altogether, but as of Friday afternoon we were able to go through the process online without being told of any issues. A call to Apple's hotline, however, yielded only an apologetic message about high call volume.

The iPhone 5 is also available for pre-order from Best Buy, Walmart and other retailers, as well as from Verizon Wireless, AT&T and Sprint Nextel. Lines form at stores on Sept. 21. Analysts estimate that Apple can expect to sell 50 million iPhone 5s by the end of the quarter and year.

Son of a Glitch?

Given the history of iPhone glitches, such as the antenna issue that prevented Consumer Reports from recommending the iPhone 4, some consumers may choose to wait until the first 10 million or 20 million customers field-test the iPhone 5.

But wireless analyst Gerry Purdy of MobileTrax told us the high volume expected by Apple, plus the fact that it is not a major redesign of the product -- though it is thinner, lighter and taller -- suggests that glitches are unlikely.

"This is a refresh of the product, rather than a revolution or innovative product," Purdy said. "They wouldn't be into a run-rate of -- to be conservative -- 40 or 50 million units unless they felt it was pretty stable."

He added that concern about potential glitches or malfunctions has likely kept Apple making only incremental improvements in the device, including the increased screen size and a radio for long-term evolution high-speed data . Expectations for near-field communication for mobile payments, however, fell short.

"In technology management you have to be able to reduce the risk of failure and at the same time make sure you can produce large volumes," Purdy said.

Reducing Risk

Apple might have gone for a better camera or an even larger screen size – 4-1/2 inches is becoming standard for smartphones -- or introduced a more high-performance connector than its new Lightning cable, but that might have been too much risk. This year's changes, however, were necessary to keep up with competitors, Purdy said.

The next full-refresh iPhone will have to introduce something very big, similar to the Siri voice assistant added to the iPhone 4S, in order for Apple to "keep up the magic," he said.

Meanwhile, "the Apple fan base is happy and staying within the walled garden."

In a sign of just how popular the iPhone is growing, there's a substantial market for older models. They can be sold via eBay, Amazon or Gazelle.com or at a GameStop outlet or to Apple or Verizon Wireless, depending on the model and condition of the device.