I set up the flaps on mine. But I really cant tell you how effective they are, cause it seems every time I plan on doing something I forget as soon as the wheels leave the ground and I end up flying around all willy nilly like. I have just 3 flights on mine so far and I just managed to get the flap to elevator mixing right, Its 12% down on my futaba 14sg. The times I did put the flaps down I was just checking for pitch changes.
On the video I posted it shows the flaps down when my engine stalled, and all I can tell you about that is that the plane remained perfectly controllable and I might have been able to turn even father. But not having a good feel for the plane it was better not to stretch it. Out of the 3 flights I can tell you the plane has excellent slow flying characteristics, And the flaps are not needed. I don't have any experience with flaps so for me its something I get to mess with and learn how to use. I believe the manual says that too.