I will probably always switch between circuit training and lifting heavy. I've gotten the best results from those two. The only time you'd see me on a treadmill is during a recovery phase where my legs are really too sore to do anything else.
Yea, couldn't imagine a treadmill ALL of the time, but I would like to add fast walking soon and not have to worry about weather conditions.. I have been going crazements on yard stuff this week & added lunges and squats just today. My legs are effing horrible for endurance as compared to my upper body. It's like two different people in one body.