Re: needing a little more answers :)
Moms who can feel their letdown sensation often describe it as a tingling sensation. But not all moms feel their letdowns! I have nursed 2 babies and never felt a letdown. Also, many moms who feel their letdowns in the beginning, when their supplies are at their most abundant, eventually experience a lessening of the sensation, or even have it disappear.
ETA: a mom may be able to determine when she's having a letdown by watching her baby. When the baby's sucking transitions from a "suck-suck-suck" to a "suck-swallow-breathe, suck-swallow-breathe" pattern, that's a letdown.
Coolest thing my big girl said recently: "How can you tell the world is moving when you are standing on it?"
Coolest thing my little girl sang recently: "I love dat one-two pupples!"