We also used the Playtex Nursers (brown nipple) with both daughters (both breastfed) and they seem to work perfectly- they don't leak or pour when you hold the bottle upside down (as do the Medela nipples), the slow flow nipple was perfect, and the shape/texture of the nipple seemed to be just what both of my daughters liked. We tried the Tommee Tippee ones with our newest daughter and they leaked all over the place! Plus, they are a funny shape/size and didn't fit well in any cooler we owned.
I also love that the Playtex bottle opening was large because it was easier for me to pour milk in without spilling it. Silly, but definitely a plus for me. (Especially if you have to pour from the Medela bags!)