I think it depends on the baby. Did yours respond well to swaddling? That (and the various gimmicky swaddle sacks) was the only way I could get my DD to sleep before 6 months and now, at almost 18 months, she is still in the armless sleep sacks and cannot fall asleep without wearing one. I love the Halo and Aden and Anais ones and definitely think that they are worth it. I got the extra larges when she was about 6 months old and she still has room to grow into them.
Okay cool. I just wanted to make sure it wasn't something that might benefit him in terms of warmth. He seems to do just fine at night in a sleeper and a blanket when needed. He loved being swaddled. My mom still wraps him up in a swaddling blanket when he sleeps at her house.
LOVE them. I used one on Natalie until she was in a real big girl bed (a double, not her toddler bed), so until she was almost 3. They make them with holes cut out in the feet for bigger kids to be able to walk around, and are perfect for a kid who is alllll over the bed, but gets cold at night (especially in cool climates, and in winter) and is too young to know how to put their blankets on themselves in the middle of the night.
Another bonus: if the kid is into taking off their pjs and diaper, you pop them in one of these things, BACKWARDS, and walla. No more toddler naked time at night. Unless they're a ninja. Then you're out of luck.