Can talk only about the node.js runtime with native add-ons. Using it for various automation tasks less then 100 invocations a day where it is the most convenient solution out there for peanuts. We also use it for parsing Swagger/API Blueprint files, here we talk 200k+ invocations a day and works great once we figured out logging/monitoring/error handling and limited output (6MB). We do not use any framework because they mostly are not flexible enough but apex (http://apex.run/) and serves us well. We've hit couple of times some limits but as it is invocation per request only some calls failed and the whole service was unaffected. I see the isolation as a big benefit you get. One thing which sucks is that if it fails (and it is not your code) often you have no idea why and if anything can be done. We use it together with AWS API Gateway and the Gateway part is sub par. The gateway does not support correct HTTP like 204 always returns a body and god forbid if you want something else than application/json. To sum it up lambda is great with some minor warts and the API gateway is OK but can easily imagine it much better.
The project was created for a talk I gave and because lot of people asked for some more material I've published the code as well as some documentation on the Linux features etc in the hope that it will help more people to grasp what the containers really are.