Pete,
You might be very surprised at how good they are. The caveat to that is where you are located and therefore what the ducks have been eating. I have heard that mallards feeding on salmon carcasas out west are inedible and that brant are horrible. But you talk to someone in another area and those same species are their favorites. Personally, I'll trade any mallards I get for GE's shot in my area. Other than teal or woodies, I'll take GEs over most any other duck.
Proper preperation is the key:
1) After shooting them lay them on their backs immediately.
2) Age on their backs for several days either outside or in the frig. I will be cleaning ducks today (Weds) that I shot on Sunday. Aging really works to tenderize the meat and I think minimizes the gamey flavors.
3) Breast and soak the meat in salt water or baking soda water for a minimum of 24 hours and more if they might be strong.
If you suspect you have a strong bird soak in Pineapple juice after the baking soda water.
4) DO NOT OVERCOOK - medium rare at the most. Flash fry, grill, deep fry, hot oil fondue, etc.
One of my favorite recipes that is quick is to make a pocket in the breast, dust the inside with curry and stuff with blue cheese. Tie up or skewer and roll in seasoned flour, I like cajun. Pan fry in olive oil until brown. Pour off excess oil and put the pan in a 300 degree oven for an additional 8 minutes.