This is a great idea and I was really hoping it would work well with my three month old daughter.  First I have to say the instructions are horrible, it gives very little information on how the sling should be adjusted or rather how it should fit your body once you've adjusted it.
No matter what I did or what position I put my baby in she just looked so uncomfortable.  Facing forward I felt like she was going to fall out of the sling. This position also seemed dangerous because the front of the sling would sit right at her throat. In both the forward and the 'hug' position her legs looked bunched up.  In the cradle position her little chin looked pressed against her chest... it has horrible head and neck support.  Bottom line I wouldn't carry my baby in this.  Big disappointment especially for being endorsed by Dr. Sears.  I would highly recommend the ergo baby carrier instead.  A far better product, its worth the extra money.