re: If you saw this in your gym, your thoughts/opinion would be...?

It isn't considering you are taking balance and stabilization muscles out of the equation with a sled. Only about once a month I tread into that weight range with a sled on a heavy day. Most of the time I stick to alternating between squats and leg sled but doing low weight high reps (5 sets of 12-15 reps of squats and 5 sets of 15-20 reps of sled). I do that with no break between the squat and sled so it acts very much like a cardio workout.