This past year has been one of the few I've gone over 100 orders on Amazon. This holiday season, most deliveries have arrived early or no later than on-time. Earlier in the year, there were a few problems with stuff showing up late or getting "lost" for a couple of days, but the Amazon delivery drivers have gotten much better delivering packages. I did have one problem this year, a package that never arrived, but I could not get a refund through normal processes. And yes, it was one of those prime, "guaranteed two-day delivery" items. After ordering, it got bumped to two weeks and would have been delivered while I was on vacation. So I try to cancel the order, which kicked off a multi-week process with one of the most helpful support people ever. Seriously. Amazon's support people have been amazing.
I tend to order Amazon- or name-brand nutritional supplements, clothing, small electronics, hard-to-find, non-perishable foodstuffs, and small tools from Amazon. I try to make fewer, larger orders and use their once-a-week delivery day.