In 2006, it introduced two new products: Guinness Red, an ale-style beer available only in Britain, and Guinness Mid-Strength, a lower-alcohol version of the original (2.8 percent versus 4.2 percent) sold in just a handful of Dublin and Limerick pubs. Mid-strength is targeted at the "Celtic Tiger" business crowd who may want a pint or two but have a big meeting in the morning.

All the effort has resulted in a slight uptick in young imbibers, but Guinness still faces a fundamental challenge in recapturing its former stranglehold on the Irish market—what Stirling calls a challenging flavor profile. It's called "stout" for a reason. "It starts out creamy and finishes with a slightly sour twist," says Julie Johnson Bradford, editor of All About Beer magazine (allaboutbeer.com). "The beer has a slightly burned-toast flavor that's quite refreshing." Try selling that to an appletini aficionado.

Also detracting from the cheer is the fact that last summer's dreariness contributed to Guinness' success—the beer is much more popular in colder months. Stirling says the inclement weather was a prime reason for the growth, while Mackin says that it only accounts for a third. Either way, depending on rain to increase beer sales is ill advised, even in Ireland.  

The news isn't as damp outside of the home country. Globally, Guinness sales were up 6 percent during the second half of last year, and there has been strong growth in developing countries. Nigeria, where Guinness opened its first brewery outside the British Isles 46 years ago, is the third-biggest market after Great Britain and Ireland. Celtic history matters little in Africa, where bottles of Guinness Foreign Extra Stout have 7.5 percent alcohol content and are postured as a macho, virile beer. The beer is spreading throughout the continent, and in the same six-month period overall sales in Africa were up 14 percent.

Guinness is also doing well in North America, but Olly Wehring, managing editor of beverage trade website Just-Drinks.com, thinks it could be doing much better. "Guinness needs to look more seriously at the United States," he says. Traditionally, Guinness has sold well in Irish enclaves on the coasts and Chicago, but Wehring sees an untapped reserve in Middle America. "Craft beer is growing across the country, and Guinness should jump on that bandwagon."

No matter where the growth markets for Guinness are, though, Ireland will always be the land of stout and honey. The country and the beer are synonymous, so it's important Guinness maintain the "good craic" at home heading into 2009—after all, next year marks the 250th anniversary of the founding of the brewery. Even that cabbie should be toasting his old man and the old country…with a pint of Guinness.