UGH, I have a serious love/hate relationship with Sam's. We have both Sam's and Costco memberships and both have their ups/downs.
Things I like about Sam's:
They offer a premium membership with extra discounts and yearly cash back
They have different products than Costco
They offer self checkout, so you aren't stuck in a long line with only 1 item
The photo department is worth the cost of membership alone - we regularly order prints from here and also had custom birth announcements made. We paid $12 for 50 of them, which cannot be beat.
Overall, it's fine. Kind of like a necessary evil, but since it's closer than Costco and they also offer cheap gas, we'll continue to be regulars. We haven't had to buy diapers yet, but this is where we will do so because it will save us a ton of money.