Provides a distinct citrusy grapefruit flavor and aroma which can be used as both a bittering and an aroma hop. Good for dry hopping as well. The quintessential American hop. Sierra Nevada Pale Ale is a showcase for this hop. Centennial and Columbus have a similar aroma/flavor, but are considerably more bitter.
Citrus bomb pretty much sums it up. It is a high alpha version of Cascade, but slightly more pungent. Can be used for bittering anywhere you would use Cascade, but as an aroma/flavor hop, it can be quite intense due to the high essential oil content (can be as much as twice the typical oil content of Cascade), so compensate accordingly. Centennial is the star of Bell's Two Hearted Ale.