Apple stock plunged in afterhours trading, falling over 5 percent, on news that CEO Steve Jobs is stepping down due to health concerns.

Jobs said: I could no longer meet my duties and expectations as Apple's CEO.

His retirement isn't entirely unexpected, ever since he took his third medical leave from the Apple CEO position earlier this year.

Going forward, COO Tim Cook will take over the CEO position, while Jobs will continue with Apple as the chairman of the board. 

Investors sold Apple shares because Jobs is seen as pivotal to the revival and phenomenal success of his company. He took Apple beyond its original computer business and carved on a multi-billion dollar empire from the iPod, iPhone, and most recently, the iPad.

What Jobs did was far from routine; many call his feat of transforming Apple in the 2000s as genius.

Analysts, however, generally do not seem too concerned about Apple's future.   

From a longer-term perspective, we believe Apple's strategy is well laid out and believe Cook and mgmt team will continue to execute, wrote analyst Maynard Um of UBS in note.

Apple knows what it's doing for the next big thing, maybe the two next big things. They lose the showmanship of Jobs, but [the company's executives] have their marching orders, said Ezra Gottheil of Technology Business Research, reported Computerworld.

Analysts were equally optimistic when Jobs took his medical leave earlier in 2011.

Hedge fund star David Einhorn, in a Bloomberg TV interview soon after Jobs' announce of medical leave in early 2011, brought up another bullish argument for Apple.

He said Apple was trading at only about 14 times its earnings (back at January 2011 levels) when one takes into account the billions of cash the company held.  However, premium companies like Apple have historically traded as high as 80 times their earnings.

With the stock trading, net of the cash, around the market multiple, [Steve Jobs' health] isn't the sort of thing that one needs to worry unduly about, said Einhorn.