In most airplanes I do not recommend the use of Flaperons, Now dedicated true flaps yes thats a different matter and can serve some useful purpose in aiding in the control of approach and departures.

There are other useful purposes like CaffeenMan has noted yes they are not widespread uses but legitimate none the less. In my case I have just one airplane that I use flaperons with for a very specific purpose. The airplane is a glider that I use for 'aerotow and now the chief tow ship is a Great Planes Stearman. The glider is a much modified Seniorita Cadet equiped with a tow release system, It also serves as a quick change twin engine ship with a couple of .25's but thats a different forum.

In the glider mode when under tow this very light seniorita (I have lightened the stock structure significantly with undersized lumber) tends to overclimb the tow plane at its lowest functional tow speed so the ailerons I have used are full span and will reflex up to 15 degrees up and this helps considerably under tow and after release the flaperons are returned to in trail or 10 degrees down if desired.

John