Huh. I'm usually the first one to complain if any meat is "too gamey" or something weird, but I don't remember mergansers being any "worse" than other ducks. Maybe I just don't realize what a brilliant chef lokidog is (he generally cooks it...although I have developed my own "Kelli duck" recipe). Well, since we have some fresh merganser, I guess I'll get a new taste test. 
Just don't try orange sauce on it. My mother would try and get us to eat duck with orange sauce. Almost make me puke each time. Might be OK on pen raised birds, but we lived on the Siletz bay and fishy mud oranges ain't no good! Apple sauce, real butter and tarragon have been my go to on muddy ducks.