I'm so glad you asked this! I
just built a service on API Gateway + Lambda in the past two weeks. Here's my unstructured thoughts -
* I love that I don't have to provision any resources. The fact it will scale to volume automatically is a huge win.
* Lambda was a treat to work with. We used it with Python. Both the web console and API interface worked great for us.
* I was able to get Lambda development working end-to-end with a Makefile and the AWS CLI.
* API Gateway was a bear to work with. The concepts are unintuitive, the interface sucks, and the logging is lackluster. I found it difficult to go through the develop/test/deploy cycle on because of these issues.
* API Gateway is brand new. Brand new AWS services have bugs. We hit bugs.
* API Gateway documentation is awful.
* API Gateway had a bug where it stopped logging. If it doesn't log, it is literally impossible to debug. This hard-stopped development for 5 days while they worked on a fix.
* There's an invisible error case where your API doesn't have permissions to invoke the Lambda command. It's easy to hit and annoying.
* API Gateway doesn't support POST requests in the way you would expect. This leads to over-complicated setups for simple use cases.
* I really don't prefer the way mapping templates work in API Gateway.
Overall, our setup is humming along nicely, but it's just 2 routes. I just reviewed the Gist and I agree with many of the concerns expressed in it.