When we was first born, we tried several different swaddle blankets - some with velcro and other sleep sacks that just zipped. I was really excited to try the Merino Kids Sleep Sack because they get really good reviews and you can use them from newborn all the way through the toddler years.
I don't know if it makes him sleep any better, but it sure is a great quality sleep sack. They are made from organic cotton and it should last him until he is close to two years old. Now that he is getting hot, sometimes I only put him in a short sleeve onesie with the sack, but when it was colder out, it worked really well at keeping him warm (almost a little too warm... look out for sweaty backs - that happened to him and I had to remember to keep him out of the long sleeved onesies). The sleep sacks also make it nice for when kids are a little older because it makes it tougher for them to climb out of the crib.
The sleep sack is really good quality and washes up nice. It's a little expensive, but I think you may only need one of them, usually I will go a few nights between washes because he always has something on under it when he wears it. I also love the feel of it... it's really soft and the zipper is nice because it is completely out of the way.
Merino Kids also has some other adorable sleepwear and accessories - it's a New Zealand based company. These pictures were taken before bed - didn't want to risk waking him up after he fell asleep :)
Merino Kids sent me this sleep sack to use and review. All opinions are my own.