This was a great purchase and I am giving it 5 stars, but I ended up returning it (please read full review though).
I think I purchased this too late (my daughter was 4 months old) and she would have benefitted from it at an earlier age.  The problem-she loves to suck her thumb when falling asleep and the suit is so stiff that it wouldn't allow her to. This suit put her to sleep immediately---it was a miracle! But like I said, she couldn't suck her thumb, which caused her to wake up crying.  I returned it only for this reason, however I highly recommend this product as a great alternative to swaddling.