Putting in my 2 cents, I just ordered four pounds of whole hops from hopsdirect (before they put up the amarillo, darn it!) and when they got here I dumped some into two kegs I have lagering in my keezer. I have had good experience with whole hops and dry hopping but when they are this fresh I am getting a fairly strong "weedy" or grassy flavor along with the other desired attributes. I took one bag out after four or five days, and the taste is subsiding. So one of the knocks against dry hopping with pellets is the "vegetal" taste, but here I'm getting it with whole hops, go figure.
I used to be a whole hops all the way kind of guy, but pellets are just so convenient for use and for storage. If you read Designing Great Beers, there is a table in there that establishes that whole hops have roughly 80% of the bittering power of pellet hops. I have found this to be pretty accurate.