If you mean the kind where you lie on your side and lift the top leg up and down, I think all you get is tired.
I do some kind of ballet/Callenetics leg stuff at the cable station with a cuff around my ankle. But, I think I'm probably the only person in my gym doing this stuff. I do side extensions, back kicks, etc. But these are just little things compared to leg press, calf raise, etc.
I do a sort of isometrics move for my inner thighs--sit on floor facing stationary object, put legs on either side of said object and push!