They are mega handy. The bigger ones are best - 120cm x 120cm. You may use them for day sleeps if you have some warmer days or if bubs is wearing a really warm jumpsuit or something.
I had a summer bub, but this one will be winter. I am planning on using them.
ETA: That's if I can convince DD to share, LOL! She still takes a wrap to bed with her to cuddle