I actually tried this and did it for 30 days. I documented the results on my blog. Here are the links to my articles:
Find out if Bowflex and MuscleTech Supplements Work 30 Day Workout Trial Results - Week 1 & Week 2 Have FUN exercising on a treadmill!
and the results here:
Bowlfex Kicks Butt, 30 Day Results
In the results I show the difference in my Body Fat %, Weight, and Amount of Weight I was able to lift.
I hope it helps to answer your question.