My 3.5 year old uses one occasionally, and does really well with it but 80% of the time she uses a straw cup with a lid. We bring water to all areas of the house, or out and about with us it just makes sense. My youngest (almost 2) can use one with minimal liquids in it but usually we stick to cups with lids for her.

Does your LO use a cup without a lid most of the time? I'm curious when kids transition to those for good, or if it's more cup preference.