I do cardio 5 days a week for 45 min (just long enough to watch an episode of something on my PSP

Those 5 days, I also do strength training beforehand. I rotate between 3 muscle groups (legs, upper body, abs/waist/back), about 15-20 minutes per muscle group.
On the 5th day (Saturday) I do 2 muscle groups so that I've worked all groups twice that week. (I go Mon-Thurs, Sat) It works out so there are at least 2 days of rest between each muscle group workout.
I do 3 sets of 15 reps. I'm doing enough weight so that I feel burn at the end of the first set and I'm ready to give up about halfway through the last set.
Any comments, suggestions?