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.