Each to their own, but 9 quid a month (or £95 for a year) is a hell of a lot to pay for a few quick deliveries. For me that would be a very poor bargain.
I don't buy stuff from Amazon if I need them urgently, and am willing to wait for a delivery. I _do_ have a problem with being offered goods at a certain price and delivery timescale at the point of sale - only to discover they significantly change the deal once I am committed to buying.
I recently had an ebay item where Evri told me they had received the goods from the supplier - but the item didn't budge from their receiving depot for another 10 days. That was supposed to be 48 hour delivery.