On Wednesday, Apple said initial quantities of the iPhone 7 Plus have sold out globally. The smaller iPhone 7 has sold out in the new jet black color, the company said.
Also this week, T-Mobile and Sprint both said demand for the newest phone is up significantly.
Sprint announced pre-orders of the new iPhones were up more than 375 percent in the first three days compared to last year. T-Mobile said pre-orders are up nearly four times compared to pre-registrations for the iPhone 6S and iPhone 6.
"It's still early, but the results out of U.S., particularly T-Mobile and Sprint, look encouraging and perhaps suggest that they can, in fact, grow year over year in '17, which would be big for the stock," Power said.
Rod Canion, co-founder of Compaq Computers, said he's one of those who buy a new iPhone every time one comes out. He believes the company is "on a roll right now."
However, while Tim Cook is doing a "great job," he's going to have a tougher road than Steve Jobs, said Canion, who is featured in a new documentary called "Silicon Cowboys."
"I think the challenges are different and managing a big company and continuing to encourage innovation is just something he's going to have to focus on," he said.
"There is going to be an interim period where there's just not as big of advances but they can't get behind the curve. They've got to stay up with it and lead the market as best they can."
He believes despite some good competition, Apple is up to the task.
— CNBC's Anita Balakrishnan and Peter Shacknow contributed to this report.
Disclosures: Apple is an investment banking client of Robert W. Baird.