"Convincing a company like AT&T to partner with Apple on a product unseen, convincing the music industry that this is the wave of the future and they have to get on board" were both significant accomplishments, he said.
The drop in share price will be muted because rumors about Jobs' health have been circulating for months, Hargreaves said. "I think anyone that's been buying the stock in the last couple of months has been keenly aware that his health is an issue," he said.
Cook is thought to be a good choice to run the company during Jobs' absence, although he's not the person who will develop Apple's next iconic product.
"Tim Cook's the guy who makes the trains run on time. He's not the creative genius," Kay said. "Even though in some sense he is an excellent manager and is the backstop for Steve ... that's not going to do anything except make the trains run on time. That's not going to decide what the train should look like in five years."
Still, Jobs' absence is unlikely to affect short-term product plans, which will already have been decided, Kay noted.
(Agam Shah and James Niccolai in San Francisco contributed to this report.)
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