We tried it at a meeting. Both leaf and pellet mostly pellet. Right before consumption. Waited maybe 5 mins. Screws the carbonation up, makes it flatter and foamier.
Well I wasn't too impressed, but it was interesting. Citra came out ok but mostly hmm...
I tried it last night. Filled the french press with my IPA. Put in a handful of Cascade leaf from the freezer. Waited about 5 minutes. Nothing. I think cold beer and frozen hops equals no extraction at all. Oh well. It sounded like a good idea.
I've added three Oz to a French press before and let it sit at 180 for like 20 min. I then put it in a five gal batch. Didn't notice much difference. 3 Oz of hops soak up a lot of water.