Used it a couple of times for a few bits&pieces that happened to be cheap.
Very variable pricing - the same stuff can halve/double in price over a day or two - when it's cheap it's very cheap, but you need to be vigilant over price changes. Look for items that generate 'free delivery' - often worth adding them just to save the delivery cost. Note that Amazon Prime does not give free delivery on Amazon Pantry.
Deliveries are by Amazon's own vans - the same as used for other goods - which means that you don't get any accurate delivery times - just a whole day or evening. I don't think the packing is very good - I've had some scratched/dented stuff - refunded, but still a pain.