while this is an old thread, i feel i need to reply in someway. there are many factors that can contribute to your hops in the boil whether it be early additions, late additions, cohumulone, alpha acids, etc. in any case, i would never compare the bittness level of say 60ibus w/ a 60 addition to a 60ibu with a 5 min addition. we have done several tests in the matter of bitterness, flavor, and aroma additions with highly scaled additions at each time. throwing in different hops varieties w/ different oil content can play a huge part as well. alpha acids apart, 2oz of chinook at 60 is not the same as 2oz of simcoe at 60 IMO. without throwing too much controversy on this topic in the mix, i believe the key to make a great IPA (thats what we are talking about, right?) would be using a blend of high cohumulone and low cohumulone hops at 60 (or just a smaller amount of high) and a ton of low co hops at 20-knockout. just my IMO...