I've been contemplating this same question for months (10 to be exact) and during an unscheduled stop at Creative Kidstuff the other day and noticed these. Bought them immediately and they are amazing!!!!! Sock Ons are the way to go for sure.
I use 18mo socks on our 4 month old - the ones her sister just outgrew. The don't look too goofy & never fall off.
this is what we do. millie has heck trying to get them off lol! we have the 18-36 mo size and fold them over. i originally got then because the socks in her size cut the circulation off of her fat legs/feet.