NEW YORK (CNN/Money) - Early enthusiasm for shares of AOL Time Warner faded to a more muted optimism Monday as investors, digesting the news of Chairman Steve Case's resignation, mulled over what's next for the company.

"It will put a short-term top on the stock," said Seth Tobias, manager of the hedge-fund Circle T, of Case's resignation. "I think it marks the end of an era -- the last remnant of excesses and looking at fundamentals through rose-colored glasses. Now people are going to look at AOL and value it as a media conglomerate and find it's fairly valued."

Although he has both owned and shorted AOL in the past, Tobias currently has no position in the stock. Up more than 4 percent in pre-market action, by late morning AOL Time Warner (AOL: Research, Estimates), parent of CNN/Money, was up just 27 cents, or 1.8 percent, at $15.13.

For many investors, Case has long been a symbol of everything that was wrong with AOL Time Warner. The company's stock has plummeted since the 2001 merger of America Online, which he co-founded in 1985, with Time Warner. With hindsight, many investors believe that Time Warner would have been better off if it had never listened to AOL's overtures -- that Case had pulled a fast one, trading in his overvalued America Online shares for undervalued Time Warner ones.

"The question was not whether Case would leave, but when," said Credit Suisse Asset Management managing director Stanley Nabi, who holds shares of AOL.

Doug Kass, a hedge-fund manager with Seabreeze Partners who has a small short position in AOL, thinks that Case's resignation is a negative signal, indicating that the online unit will show a net reduction in subscribers when it reports results Jan. 29. "That's going to shake the Street," Kass said.

Other observers feel that Case's resignation does little more than give the stock a psychological boost, but CSFB's Nabi believes that it, like the resignation of Chief Operating Officer Robert Pittman in July, signals the company is "clearing away the rubble" of the busted deal. He thinks that there's a better than 50 percent chance that the company will scuttle its ailing America Online unit.

That will take time, however. The company is committed to turning the Internet business around -- and indeed it must if it wants to either sell it or spin it off in a public offering. In August AOL Time Warner hired Jonathan Miller, formerly president and CEO of USA Information and Services, to take on the reins at America Online.