A friend recommended the miracle blanket to me so I bought one before my baby was born. I also bought a plain triangular swaddle and was given a swaddle with velcro from NCT. I have found that these other swaddles do not contain my baby and he can easily kick his way out. The miracle blanket has special pockets and flaps so that it's really easy to use. You put the baby's feet into a pocket, then you use a couple of flaps to hold its arms before using the main lengths of the swaddle. Miracle blanket's own website has a video of how to do it and I found it really easy.
I have found on many occasions that this blanket calms my baby and soothes him off to sleep. The blanket itself is made of thick cotton rather than being of a blanket material. However, I have found that in the heatwave we have been having lately that he can get too hot so you have to make sure that the baby is wearing clothing suitable for the temperature (I have had my baby in a nappy with the windows open so that he doesn't overheat.)
My baby is now almost 14 weeks old. I think the blanket is supposed to be suitable until around that age. My baby is long and outgrew the swaddle a few weeks ago. However, I can still use it so long as I don't tuck his legs into the pocket. I find that swaddling his arms still helps to get him off to sleep.
I liked the miracle blanket so much that I bought 2 (in blue and white). I like that it doesn't have any ties or velcro and is easy to use but I think it would be even better in the winter when I wouldn't have to worry so much about a hot baby!