I already have Amazon Prime, so adding Amazon Mom to the account didn't cost me anything extra. I haven't really had the chance to use it yet (my son won't be here until September), but I'm anxious to try it just for the convenience factor. I would say that their prices as far as things like diapers and wipes and formula are concerned seem fairly comparable to Costco/BJs. I still have to do some research into whether or not other household-type supplies are a good value, but I'm sure it will be nice having at least the baby essentials auto-delivered every few weeks.
Re: Amazon Mom