I love it - ammonia smell means it's past its best and personally I'd bin it. It doesn't like being frozen, according to my fishmonger and it'll turn very quickly.
I cook it in the oven in tinfoil with lemon and garlic and a bit of olive oil, but the fish is not the most attactive colour cooked like that it must be said. It presents better if it's crumbed or floured and either grilled or fried and then capers, lemon, and buttery juices as everyone els has said - oh yes and mind the prickles on the skin whilst dealing with it - are we selling this one or not? Seriously - it is a really nice fish and the advantage of no nasty bones, just cartilege.