My two year old grandson is moving full speed from the time he gets up in the morning.  In the house we mostly wear our socks with no shoes and previous socks purchased for him have always had a tendency to either slip on the hardwood floors, regardless of the 'grip', and/or to wear down and partially come off.  The Hanes are great.  They are stretchy so they fit wonderfully, and THEY STAY UP and ON, and the grip seems to be working very very well.  Highly recommend them.

Revision four months later.  We still recommend them, however we recommend that you buy larger than you need.  We find that washing shrunk them somewhat and between four months of a toddlers growing and the shrinking, he's already grown out of them.  We do still like them and have purchased some but purchased the 4T size.  Hopefully they will last a bit longer.