Concluding its third study of Apple iPhone users, usability market researcher User Centric has found business users typically will have a tough time with the mobile phone while consumers will adapt to the device smoothly and quickly.

"It's very clear," said Gavin Lew, User Centric's managing director, in an interview Wednesday. "Business users, people who use e-mail a lot, will take a tremendous performance hit. Even with all the nice features."

On the other hand, typical consumer users will find little difficulty in switching from a conventional 12-key mobile phone to the iPhone and maybe even find a slight ease-of-use improvement.

Collecting data from 60 participants -- 20 iPhone users, 20 numeric phone users, and 20 hard-key QWERTY phone users -- User Centric asked all participants to enter six fixed-length text messages on their phones.

User Centric found that while iPhone owners entered text as rapidly as QWERTY owners, they made significantly more texting errors, 5.6 errors per message compared to 2.1 for QWERTY owners and 2.4 for numeric phone owners. "While the iPhone's corrective text feature helps, this data suggests that iPhone users who have owned the device for a month still make about the same number of errors as the day they got it," Lew said.

Can the problem be fixed? Lew was asked.

"Apple could space out the keyboard," he said. An outboard keyboard would likely be too cumbersome, he added.

User Centric's studies on the iPhone revealed that consumers have found much to like about Apple's phone even beyond its much acclaimed music player capability. The iPhone is more intuitive than other mobile devices, for instance, helping even novice users to adapt quickly to its use. In comparing texting performance between iPhone owners and novice non-owners, User Centric found no significant difference in error rates.

But, in comparing user performance on unfamiliar phones, the market research firm found that numeric phone users could enter text faster on a hard-key QWERTY phone than on the iPhone. They also made fewer errors on the hard-key QWERTY phone.

"The iPhone is a great switch from a numeric phone," Lew said and cautioned: "But if you're switching from a hard-key QWERTY phone, try the iPhone in the store first."