I started with a manually-packaged Python function and credstash [1] to store credentials for non-AWS services. It gets invoked nightly by CloudWatch and has been bulletproof for months. I recently built a microservice [2] for Election Day with Flask and deployed it behind API Gateway with Zappa [3]. Lambda isn't for every use case, but for those it is, I'm bullish.
[1] https://github.com/fugue/credstash
[2] https://topics.arlingtonva.us/2016/11/voter-registration-sea...
[3] https://www.zappa.io/