Flaperons do work however, when used on a high wing loading airplane such as many scale builds they can cause tip stalls. Often they work fine but it depends on the plane your using them on. They do increase the angel of attack of the whole wing and it is not a good thing to do at the wingtips unless you are looking for a snap roll.
If you don't believe this look up flaperons in the aerodynamics forum and look at the comments from those with lots of knowledge about this issue.
One scale planes they are one of the fastest ways to get a plane back into a kit.
Fully functional flaps are still the best way to go period. Although using the flaperon set up as spoilers is a good method for lightly loaded airplanes.
But that is only my opinion