Former S3 employee here. I was on my way out of the company just after the storage engineering work was completed, before they had finalized the API design and pricing structure, so my POV may be slightly out of date, but I will say this: they're out to replace tape. No more custom build-outs with temperature-controlled rooms of tapes and robots and costly tech support.

If you're not an Iron Mountain customer, this product probably isn't for you. It wasn't built to back up your family photos and music collection.

Regarding other questions about transfer rates - using something like AWS Import/Export will have a limited impact. While the link between your device and the service will be much fatter, the reason Glacier is so cheap is because of the custom hardware. They've optimized for low-power, low-speed, which will lead to increased cost savings due to both energy savings and increased drive life. I'm not sure how much detail I can go into, but I will say that they've contracted a major hardware manufacturer to create custom low-RPM (and therefore low-power) hard drives that can programmatically be spun down. These custom HDs are put in custom racks with custom logic boards all designed to be very low-power. The upper limit of how much I/O they can perform is surprisingly low - only so many drives can be spun up to full speed on a given rack. I'm not sure how they stripe their data, so the perceived throughput may be higher based on parallel retrievals across racks, but if they're using the same erasure coding strategy that S3 uses, and writing those fragments sequentially, it doesn't matter - you'll still have to wait for the last usable fragment to be read.

I think this will be a definite game-changer for enterprise customers. Hopefully the rest of us will benefit indirectly - as large S3 customers move archival data to Glacier, S3 costs could go down.