I've been experimenting with Zappa hops in the last couple of batches. I have to say that they are definitely unique and best used with a light touch. Zappa is a weird hop. As it warms up, I'm getting hints of hazelnut, stinging nettle and dandelion sap. It does not work all that well for pale ales, but it integrates OK in fuller beers, like a double IPA.
As far as dry hop usage goes, 2g/l of Zappa is at the heavy handed end of the spectrum, where the same base beer (Double IPA) can easily take 5g/l of Citra. The character was quite pronounced for the first couple of weeks, but after a month it mellowed out and adds a pleasant complexity. It may be a good hop to try in a barley wine.