AWS Lambda is really cool, but there are a few quirks to keep in mind that make it not a general replacement for something like a box running nginx + uWSGI, etc.
There was a nice 45-minute talk given at PyOhio this year by Matt Land that covers most of the tradeoffs around running Lambda in prod.
AWS Lambda: From Curiosity to Production
Abstract - http://pyohio.org/schedule/presentation/246/