A woman who used to babysit for me used it. It worked really well for her daughter. But my kids didn't take to it. My oldest is very smart, but said it was boring (I think she was too old for it honestly - she was 3) and my younger daughter didn't take anything away from it. She didn't want to sit and watch it... she doesn't watch much tv. It truly depends on the child.
This question must get asked 3-4 times a week. lol. IMO. they are not learning to 'read' they are learning sight words. they will start school in the same place as every one else needing to learn phonics But with no ultimate goal, reading.