I just purchased one and I think it is the best gun I have ever owned. I dont think 3.5 inch is needed for waterfowling, you can do just as much with a three inch gun and the right chokes.
A while back I ended up buying a 3.5 inch gun and found myself using 3.5 shells maybe once a year. I do not think it is neccesary for a 3.5 inch gun I think you can do the exact same with a three inch gun.