Not a fan - rarely do people do them correctly to get the benefit that Saibot mentioned. A more effective exercise (imao) is the step up. Put a bar on your back (a shorter bar - like 30lbs) and load it up. Step up onto a bench or step (just so thigh is parallel to floor when stepping up) with one foot and stand up on the bench without letting the other foot touch (you can knee up or just leave it hanging behind). You'll see people doing these with dumbbells and leaning all over to get up on the step. Use a bar and it will ensure your form is right on. If you want to do lunges do them for two reasons: loosen up the hip flexor, jump lunges for HITT. just saying...