useful? sure a little.. if you have weak adductors/and glute med+TFL, it definitely can help strengthen them..
all of those machines can be useful to some small degree.. being able to isolate lagging muscle groups can be effective.
one of the problems with machines is how they can create imbalances or alter 'firing patterns' which can negatively impact performance.. but for the most part that's an extreme circumstance.. for example, if you aren't free squatting/free lunging, and are just performing lots of leg extensions, you're going to have problems.. but throwing in a little accessory work on isolation-machines, isnt a problem.
pc