ORIGINAL: tonyob
There is really NO benefit (except that you don't have to cut separate flaps) but they are a really BAD idea for several reasons.
Do yourself a favor and forget you ever heard the word and use separate flaps and ailerons
I think that statement is a bit too harsh and negative. I've used flaperons to good effect but they certainly aren't for beginners and as with any new technique are best practiced at 3 mistakes high. Then you can see if they help or harm your plane and what you are trying to gain with it. Most new configuration / technique / setups complicates things and breaks the keep it simple rule, but they can provide advantages in some situations that make it worth the complication.
They are fun to play with and if your in a fun fly. First time I set them up in an Up-Roar everyone told me how bad they were and I was going to crash, I liked them but i did forget they were on in one compition and just couldn't figure out what was going on. My fault and it was my first fun fly event. After a person has been flying for a while they are worth setting up and fooling around with just to see what they make a plane do. I did and in some cases they are a hoot, other times they can bite you pretty bad and quick. They sure aren't for every plane and every pilot.