iDream version 2
There's no such thing as muscle confusion. If you don't want to/seem to have hit a plateau, you have to up your workouts. For example, if you are curling 50, in two weeks, increase the load to 55 or your muscle will adapt to the 50 and not progress. Then another two weeks later, increase that load to 60 (or however much you can curl after that certain amount of time). This is called progressive overload.
Yes muscle confusion is real. Imagine touching your toes, you stretch out the muscles/tendons lengthwise. Now, put one leg out on an angle and stretch down to your toes. Your muscles are now twisted and being stretched. So instead of your muscles just stretching and regrowing in one fashion, you will have more malleable muscles used to different angles.
In response to the question, muscle confusion forces your muscles to work harder and will overall give you a better all round strength, I don't do it personally so I don't know how good the benefits are but it was recommended to me.