The API serves nearly 1 billion calls per month, with lots of variations and spikes. That, combined with my lackluster ops skills, makes AppEngine's autoscaling a perfect fit for my use case and skill-level.
Yes, it's probably more expensive than if I used EC2, but I've never been awoken in the middle of the night to need to reboot a server, troubleshoot a memory issue, or scale up my instances.
I have an AppEngine app that brings in $7k/mo with very little work, with about $2k/mo in server costs. Roughly 50 users paying between $30/mo and $500/mo
There's about 10 minutes of support work per day, but besides corporate customers occasionally needing some phone salesmanship and some manual tweaking, everything else is automated.
Yes, it's probably more expensive than if I used EC2, but I've never been awoken in the middle of the night to need to reboot a server, troubleshoot a memory issue, or scale up my instances.