Why flaked oats instead of wheat?
The first time I used the oats, my lhbs was out of flaked wheat, so I just decided to use the oats.
Honestly, there isn't much difference. There is a little less "wheaty" taste with the oats, but since you are using so little, there isn't much difference in flavor at all. There is a slightly different mouthfeel, slightly smoother. The biggest difference that I have noticed though is the clarity. The oats tend to yield a clearer beer with less haze.
Overall though, it was more a change of necessity, and I liked the results, so I went back to it this year.