I didn't give DD any nuts until after 2, but that was partly because we had a little boy over every week who was anaphylactic and I didn't want to risk it.

DD still hasn't really had peanut butter at nearly 3, but she has had nuts occasionally (mostly cashews). Seems to be fine. Again, I don't really bother with peanut butter 'cause she can't take it to preschool and I don't like to take the chance out and about with other kids.