I agree. While a dead drift is a great starting point and generally necessary to get the fly deep, some agitation is often helpful to induce strikes. Of course, the old "Leisenring Lift" is the classic method of agitation. George Daniel in his book "Dynamic Nymphing" talks extensively about leading flies through the drift and advocates leading them slightly faster than the current. He also talks about using a line loop to create drag and accelerate fly movement. I start with the dead drift, but usually try a lift at the end and / or twtiches when the fly is deep. I have found "agitation" to be particularly helpful when flies are hatching and when fishing larger nymphs like mayfly drakes and stoneflies.