- Autoscaling (but make sure you actually need this, it's easy to scale on Heroku, it's just manual)
- Based on WAR format, if you're familiar with that already (but see below)
- For play! apps the war building process is a bit of an afterthought. I had problems doing some things like custom log4j appenders and running scheduled jobs. It's not totally natural for play to operate in a servlet container so you hit some weird issues.
- Super clunky deploy process. I was basically uploading 130MB war files for every deploy via a web console. I eventually got everything deploying via a CLI build process, but it had been a big effort. I get the sensation that nobody is using elastic beanstalk but me since I used to be all alone figuring out the fairly unhealthy CLI tools. To give a sense of how to deploy a play app to beanstalk: build a war file, install some s3 tools and upload war, install beanstalk utils and use to create a new configuration, then deploy that config. There are several painful details to overcome in that list. On Heroku, you push your repo and it does it all.
- Tomcat! For example, the play didn't have the right permissions to run scheduled jobs under the version of tomcat deployed for beanstalk.
- Logging is the WORST. You can go and download captured log files for every individual server you are running. But then they never appear to contain what you need. I had 2 servers and it had been already terrible.
There's more but the short story is we're switching to Heroku and it's already been a much-improved experience. Dealing with the SSL certs, combined logging and impressive set of add-ons (loggly centralized work, websolr hosted search, etc) makes me assume it's already worthwhile.