I've heard various things (both good and bad) about Apollo, but of all the single hop beers I've brewed Apollo was one of the rare few I would be happy to drink in quantity.
I would describe Apollo as 70% Amarillo crossed with 30% Columbus. It is orange-citrus with a bit of dank. I've heard a lot of onion stories, but I've never picked it up myself.
I've used it at FWH, 60 min, late boil, whirlpool and dry hops and it works fine everywhere in my experience. I don't know if any of the undesirable flavors are related to harvest conditions, but I get my Apollo from Yakima Valley Hops, FWIW. Apollo is a staple in my hoppy American Ales.