Well I guess you are lucky then because Linode has had massive downtimes in their London and Dallas data centres in the last few days and when I was a customer their Fremont data centre went down all the time.
Not sure if the London one was really "massive", I have 12 Linodes in London all on different machines and I had one become unavailable during the downtime a few days ago and it was resolved very quickly.
http://status.linode.com
Heroku at least uses EC2 which will be far more reliable over time.