My little guy (4mos old, 9 weeks adjusted) is very willing to take a bottle, but we're having a tough time finding one that works well for him besides the disposable Similac slow flow latex nipples. Continuing to use them is far from ideal since they only last for a few uses before becoming not-at-all-slow and I have a pretty significant latex allergy.
He seems to need something with minimal or no passive flow/drip but with very little resistance to active sucking.
Tried so far:
Dr. Brown's Preemie - too difficult for him to suck from/too much resistance
Dr. Brown's 1 - too fast passive flow, chokes. active sucking resistance/flow seem about right.
Gerber Essentials Slow - WAY too fast
Evenflo Balance Slow - best so far, the passive flow is a little much and he chokes sometimes. The flow with active suck seems about right. Sadly, they don't make an extra slow or preemie option
nFant gold - too much resistance
I've been focusing on nipples compatible with narrow neck bottles since we already have a ton, but anything with pump adapters will work.