it was not a total power loss. out of 40 instances we had running at the time of the incident only 5 of our instances appeared to be lost to the power outage. the bigger issue for us was ec2 api to stop/start these instances appeared to be unavailable (but probably due to the rack these instances were in having no power). The other issue that was impactful to us was that many of the remaining running instances in the zone had intermittent connectivity out to the internet. Additionally, the incident was made worse by many of our supporting vendors being impacted as well...
IMO it was handled rather well and fast by AWS... not saying we shouldn't beat them up (for a discount) but being honest this wasn't that bad.
If the rack your instances are running in are totally offline then the ec2 api unfortunately can't talk to the dom0 and tell the instances to stop/start, so you get annoying "stuck instances", and really can't do anything until the rack is back online and able to respond to API calls unfortunately.
IMO it was handled rather well and fast by AWS... not saying we shouldn't beat them up (for a discount) but being honest this wasn't that bad.