iPhones are displacing notebooks for some, and a third of iPhone users carry two iPhones, according to a survey released on Tuesday by Rubicon Consulting of Los Gatos, Calif.

According to the author, Michael Mace, the key findings were as follows:

• One quarter of users say it’s displacing their notebook.
• One third of iPhone users carry a second phone. Composing e-mail is one use.
• iPhone E-mail is the #1 function, but reading not writing.
• About half the iPhone users are under age 30.
• Three quarters of iPhone users were previous Apple customers.
• About half the iPhone users changed carriers to get it.
• As a result, AT&T’s gamble paid off and the iPhone is estimated to have increased AT&T’s gross service revenue by about US$2B.
• iPhone users are very satisfied and use its features extensively.
• The iPhone has led users to more mobile browsing.

When AT&T and Apple announced their partnership, some in the industry said that AT&T gave up too many concessions to Apple. "The terms of the Apple-AT&T deal have not been released to the public, so it is impossible to judge its precise effect on AT&T. But based on the findings of our study, it looks very likely that AT&T made a good decision."

The report also assessed other maker’s ability to compete with the iPhone. "Apple’s type of product design is incredibly difficult for most other companies to imitate, because they don’t have expertise in tying together OS, user interface, online services, and hardware design. The path to success in smartphones is clear, but it’s not clear how many companies have the skills to walk it," Mr. Mace wrote.

Regarding the future, the report said to look for new form factors and noted that nearly half of iPhone purchasers had some request for a physical change: making it bigger, smaller, or adding a keyboard or keypad.

Finally, the report was critical of the relationship between Apple and Adobe regarding Flash, and stated that the feud needs to come to an end before another competitor uses it as leverage against the iPhone.