I used them with LO. I loved them. the only cons I can think of are that you need to buy them constantly and carry them around but its really not a big deal. I would get the target brand and it saved money. She was a lot less gassy with it, and it was easier to clean the bottle. Trick is when you put the formula/breast milk in, make sure you squeeze the drop in gently so there's no air in it... just carefully enough so it doesnt spill anywhere.