Kellerweis is one of Sierra Nevada's more recent releases.  It is a hefeweizen style beer.  Hefeweizen is an unfiltered, bottle conditioned variety of wheat beer characterized by low hop content, high carbonation and malty sweetness.  Being unfiltered the yeast is left in suspension, adding to it's characteristic flavor and cloudy appearance.

From Sierra Nevada's Kellerweis press release:

Several years ago, the brewers began working with a unique Bavarian hefeweizen yeast strain unknown in this country. This amazingly flavorful yeast was so exciting that they began working on a recipe for a traditional German hefeweizen with the Sierra Nevada twist. Traditional hefeweizen is a style that seems deceptively simple, but in reality is devilishly complex.  For years the brewers weren’t satisfied with the beer; something was missing. In a flash of inspiration, an epic trip was arranged. The brewers took a whirlwind tour through the legendary Bavarian wheat breweries to see what they were doing. It was there they realized the advantages of making wheat beer using the traditional system of open fermentation.

...

Using shallow open fermentation, the yeast has space to build layers of flavors and aroma that would otherwise be impossible.

Generally I'm not a big fan of hefeweizens.  Although I appreciate the unique and complex flavors they offer I think it's all that yeast that disagrees with my palate.  I sometimes even feel a bit congested after drinking a hefeweizen.  My uneducated theory is I'm having an immune reaction to all that fungi.

Kellerweis is one of the few (Pyramid's being another) hefeweizens I've enjoyed.  It poured a hazy golden color with a large white head.  Banana flavor dominates with a hint of clove.  This beer is sweet, smooth, and very refreshing.