A guy I used to work with smashed a bull elk in the upper left just below the shoulder with a 120 grain TSX in a 7mm wby mag. He was going for a long range shot, and that it was 927 yards. Bullet did not even attempt to open up. Smashed the leg bone, tumbled inside and did lots of damage. He found the bullet on the off side, right under the hide. It had a very noticeable bend in it.
So yes they work, but you also have to know the velocity at which it will no longer expand.