The biggest shortcoming I see compared to the other big players (AWS, Azure, Google), and it is something they don't mention, is that they only have one datacenter, compared to the several from the other big players. The pricing is quite incredible though. I suspect if enough people hop on board with this they will probably look into setting up another datacenter.
Something to note: Unless you're storing data in us-east-1, all other regions in AWS are "one datacenter". Yes, they have AZs, but those aren't datacenters, they're just compartmentalized segments of the same datacenter. So! If you can tolerate the loss of a datacenter, store in Blackblaze. If you need geo-redundancy until Backblaze can offer it? Store in us-east-1 (which is geo-redundant between Virginia and Oregon)…
Or store it in Amazon AND store another copy in Backblaze. This isn't necessarily an "either/or" question. Having two copies with two different vendors in two separate regions is probably more reliable than having two copies inside the same vendor. For example, if Amazon has a large outage that affects both your regions, you can still access the copy in Backblaze.