Adding Cardio to the Strength Training Workout

I have been doing short intense burst of cardio during the my workouts since I have begun my power phase of training. I usually do something after each circuit of exercises. It can either be jumping rope for a minute, sprinting for 15-30 seconds, riding a stationary bike as fast as I can for a mile or rowing 500m as fast as possible. Traditionally, I would do cardio at the end of a workout so as not to be so tired while I was weight training. I have also done cardio first and then gone into weight training. I really think that the intensity of the cardio session along with what exercise phase you are in (muscle endurance, hypertrophy, strength, power and power endurance) dictates how you will perform in the weight room before and after a cardio session. Since I really don't want to break up my day and do a cardio or weight session first and then come back later in the day to do the other one I didn't do first in the morning. How many of you have done this before or are currently trying this and how do you feel? Have you seen a vast improvement in your cardiovascular conditioning? Mild or None at all?