couple it with some heavy bag drills and you've got yourself a really awesome cardio session.
THIS!
I usually do 3 min rope 1 min rest (rest = doing abs) do about 4-5 rounds of this then 3 min full bag work movement, combinations, defense entire deal for about 4-5 3 min rds (try to throw min. 100 punches per round) simulate you are in a real boxing match basically. Same with kicks if you have the bags for it. Do a 50/50 split....50 punches 50 kicks in those 3 min.
Rest the 1 min off b/c you should pretty tired if you are going hard. Finish up with a couple rds on the speed bag.
I do this about 5 times a week in addition to weight training and roadwork. No way you won't be in great shape after doing this...just no way.