All of our EC2 hosts appear to be functioning fine, but they can't connect to their RDS instance which renders our app useless. If you scroll down the page you'll also see that RDS instances are having connectivity issues. Not sure if it's related but for RDS users the impact is far worse.
EDIT: We are also using multi-AZ RDS, so either Amazon's claims for multi-AZ are bs, or their claims that this is only impacting a single zone is bs.
Because RDS is built on EBS, any slight issue with EBS manifests itself as a nastier issue for RDS.
Interestingly, EBS will never return an I/O error up to the attached OS, which is likely a good decision as most OSes choke on disk errors. What this means, however, is that if something even get slow within EBS (let alone stuck), applications that are dependent on it will suffer. Most of these applications (such as databases) have connection/response timeouts for their clients, so while EBS might just be running slowly, a service like RDS will throw up connection errors instead of waiting even a bit more.
You can imagine the cascading errors that might result from such a situation (instance looks dead, start failover...etc)
I had one multi-az failover correctly, however the security group was refusing connections to the web servers ec2 security group. I had to manually add in the private ips of the ec2 instances. It appears the API issue is affecting security group to ip lookups.
EDIT: We are also using multi-AZ RDS, so either Amazon's claims for multi-AZ are bs, or their claims that this is only impacting a single zone is bs.