Also used the miracle blanket, and it was WONDERFUL. I got it at 8 weeks, and he literally slept thru the night for the first time when I used it that evening! I used it on our ds until 7 or 8 months, I can't remember now. As with Leah, once he outgrew the feet, I used it on his arms only. I unswaddled one arm when he started sucking his thumb, and then did that forever before eventually giving it all up.
But it was really worth the money in my opinion!
Good luck - and the BW Solves All Your Problems book is really great, much more info than the first!