If Lambda is able to expand the /tmp disk space from 500MB to a few GB I think that will further make the adopter better on my end. I have a requirement in which Lambda is a perfect solution except the disk space is not enough. Of course I can further divide the work into smaller chunks. If you have use distributed task library like Celery, just think of that no longer tie to your application, and you can run on event based (S3, SNS, email notification via SNS). It's quite awesome. You can probably build a public API using Lambda and API Gateway.

However, once you start using Lambda, like distributed system, testing becomes a challenge if you are used to testing everything you own in one or two monolithic codebase. I wish someone could come up with a mock version of AWS :-)