Normally, when brewing a beer you will add hops to the boil at the beginning, middle and end. With the DFH 90 minute, you are adding hops every few minutes.
Hops added at the beginning of the boil will add to the bitterness of the beer. Hops in the middle work toward the flavor and hops added at the very end are for aromas. When you are constantly adding hops throughout the duration of the entire boil, one sensation kind of blends with the next during the tasting process, I guess.
In any case, DFH 90 minute continues to be my favorite beer with Great Divide Fresh Hop Pale Ale and Pliny the Elder in a VERY close second and third.