You fart continuously while using it.

There's an episode of Justice League where Superman goes at it with Darkseid. Supes says that he always has to be careful and that the whole world is like cardboard to him, so this is the first time he can really let go.

So, you can't pick up a coffee cup or touch anyone without worrying about destroying something.

Also, you aren't invulnerable so if you punch a wall you'll still break your hands.

The minimum force you can output is now around 500 Newtons

It's extremely difficult to control - even grazing an object the wrong way with your finger can end up breaking it into pieces. Giving someone a hug can easily end with you covered in blood from the person you just split in two.

Your muscles don't gain super durability however.