I stay away from third party sellers on Amazon these days as much as possible(as in I'll look elsewhere and only come back to them if they're the only viable option) and Amazon had been getting a lot closer to regular retail for stuff they sell directly, but I still find them cheaper in a lot of instances.

I've not had problems with two day Prime shipping. They seem to have good relationship with USPS locally and things get delivered quickly and smoothly. Where I've been less impressed is their so-called "same day delivery" that has been very unreliable. The company they use here for it is Lone Star Overnight, and they drop the ball all the time, sometimes badly enough that I would have gotten it as fast with 2 day shipping. Only bright side there is that I've got lots of partial refunds and a few months of Prime for free.