The liners are very convenient to use, are available at many different stores, and are a good price. Lately several boxes have had about 6 liners with holes in them. I guess I got a bad batch. Overall they are great.

I bottle fed both my kids, and used playtex exclusively. Using drop-ins was all pros for me.
No fighting with the liners trying fit them to the bottle
Measurements right on the liners so you know exactly what to add
Measurements for both the 8oz and 10oz bottles
The liners collapse as baby feeds, so no air has to go back through the nipple
Already sterilized
BPA free
Recyclable