But some analysts question how important LTE service will be to next-generation customers, since LTE deployments are not far along in many regions of the world and LTE isn't widely appreciated by the vast majority of U.S. users.

"The wireless industry's all wrapped up in LTE, but customers don't get it," said Jeff Kagan, an independent analyst. "Most customers don't know what LTE is, and they don't care. LTE is important, but it is not what will make the difference in a [smartphone] sale or not. Customers get bigger screens, but not industry jargon like LTE."

Rob Enderle, an analyst at Enderle Group, said that because LTE coverage won't be widespread on most wireless carriers for many quarters, even in the U.S., sales of the next-generation iPhone could suffer after an initial surge in popularity.

"These new iPhones will face high pricing and poor network penetration for their key LTE feature, which could slow down adoption a lot after the initial fourth-quarter sales wave," Enderle said. "If the iPhone 5 has any weakness, it is that LTE isn't where it needs to be."

To be sure, some LTE (Long Term Evolution) users love the faster service, which can offer a dramatic 10-fold speed improvement over widely used 3G CDMA or GSM networks. LTE speeds at up to 10 Mbps or faster hasten downloads of videos and Web browsing, as well as interactions on games.