Our now-one-year-old has been walking for a couple months now. These socks (and the smaller size too) have been great for keeping her feet warm while giving her enough grip on the floor to walk without slipping.
They're also snug enough that she can't easily pull them off, which is another plus.
We've read that shoes hinder a toddler who is learning to walk, so these socks are perfect!

No cons that I can think of.