Warren Buffett's announcement last week that he is undergoing treatment for early-stage prostate cancer sent ripples through the investment world. It is still not known who will replace the irreplaceable leader of Berkshire Hathaway (BRK.B).

Investors wonder whether it's worth sticking with the company while awaiting a clue, if not a solid assurance, that the mother ship won't go the way of the Titanic.

Will it? Not likely.

Investors won't have to wait long to get answers from the Oracle of Omaha himself. Buffett will undoubtedly address the crucial questions at the annual shareholders meeting of Berkshire on May 12. In all likelihood, he will succeed in calming the frayed nerves of most shareholders during the event, which is expected to be more crowded than ever.

In the meantime, most of Berkshire's large institutional investors haven't jumped ship -- but they aren't buying more shares either.

Perhaps Edwin Walczak, a U.S. investment strategist at Vontobel Asset Management, a unit of Swiss bank Vontobel, voices the general sentiment of Buffett supporters when he argues that the stock is still undervalued.

Since news hit about Buffett's prostate cancer, BRK has pulled back, closing at $78.96 a share on Apr. 20, off from $80.70 three days before, and down from its 52-week high of $83.30 reached on Apr. 29, 2011.

"We think the stock is about 25% undervalued," says Walczak, which is part of the reason that Berkshire stock composes 3.5% of Vontobel's portfolio. "Although we are 'sympathetic' to concerns about Berkshire, we haven't sold shares -- and we're still positive, even if Buffett were to leave tomorrow," Walczak says.

Nonetheless, he is realistic enough to concede that although cancer is not the big issue, "age is and the fact that Buffett is, indeed, irreplaceable." Like other Buffett followers, Walczak agrees that Buffett's discipline and character are very much ingrained in the company's culture and will live on -- including his methodology and principles in choosing an acquisition target -- even after he is gone. Further, his cancer hasn't spread and isn't expected to be life-threatening.

The caveat, according to Walczak, is that post-Buffett, "the long-term investment case becomes less clear." There won't be another Buffett, he adds wistfully, even if he and the Berkshire board have established a deep bench of fine and strong executives.

It's easy for skeptics to advise "holding off" on buying Berkshire shares, since the stock has not been the spectacular superperformer that investors expect it to be. But I daresay it may be the best stock in their portfolios right now in terms of the long-term value of its diverse assets and the company's shining record of steady and expanding profit growth.

Berkshire is one of the most transparent companies: It discloses in detail how it conducts its businesses, what its goals are and how it intends to achieve those goals. Buffett and the board have already named an heir apparent, although his identity has yet to be announced. Plus, there are two strong backup candidates in case something happens to the chosen successor.

"Our sense is Matt Rose of Burlington Northern Santa Fe, Greg Abel of Mid-American Energy and Ajit Jain of Berkshire Hathaway Re, who were highlighted in the most recent annual shareholder letter for their contributions, are the three leading successor candidates," says Jay Gelb, an analyst at Barclays Capital.

Gelb remains positive on Berkshire and rates its stock as "overweight" with an upside case of reaching $103 a share, based on 1.4 times its estimated book value for 2012 of $76. This is near its historical high valuation since the financial crisis. He expects Berkshire will generate impressive results in its manufacturing, services and retail units, as well as in its Burlington Northern railroad operations. Berkshire's insurance and utilities businesses should also remain stable, although investment results could prove volatile, Gelb says.

But Berkshire's shares remain "attractively valued," trading at just 1.15 times 2012 first-quarter book value of $70.51, which is near a historical low.        

Berkshire has grown steadily through acquisitions, purchasing some of the most prominent names in corporate America: Lubrizol, Burlington Northern Santa Fe, GEICO and insurance company General Re. And in its diverse $77 billion investment portfolio, Buffett's stock picks also represent some of the bluest of America's blue chips, including $14 billion worth of Coca-Cola (KO), $11.8 billion of IBM (IBM), $11 billion of Wells Fargo (WFC), $7.2 billion of American Express (AXP), $4.8 billion of Procter & Gamble (PG), and $5 billion of Bank of America's (BAC) 6% preferred stock.

And speaking of transparency, Buffett has established specific principles to guide Berkshire's operations, including a long-term goal of maximizing the average annual rate of gain pershare in intrinsic business value. So its preference is to invest directly in a diverse group of businesses that generate cash and consistently earn above-average returns on capital. In acquisitions, its main principles include buying companies that are big enough, with at least $75 million in pretax earnings with a consistent earning power, good returns on equity and very little debt.

How many companies in the world can surpass or even just match what Berkshire has in assets?  

Gene Marcial wrote the column "Inside Wall Street" for Business Week for 28 years and now writes for MSN Money’s Top Stocks. He also wrote the book "Seven Commandments of Stock Investing," published by FT Press.