I've followed all the main migrations and I've say they where really quite smooth, can't remember having any major issues and each time it tended to be worth it.
I was always roughly of the mind that Backblaze was just too close to the "If it's too good to be true it probably is", seems like that may have been a good decision.
Hardly, they banned fully disposable. You can still by them but now you can swap in a refill cartridge. The price of this refillable one is the same as the original.
Many places apparently don't even sell the refills so it's practically the same.