Can I run a site on AWS Elastic Beanstalk for PHP? I'm looking at AWS Elastic Beanstalk.

Does Drupal 7 run on AWS Elastic Beanstalk for PHP?

Any extra info regarding caching and performance (e.g. comparison with PressFlow, or Memcache) is welcome.
Yes, we are currently running site build on Drupal 7 on AWS Elastic Beanstalk for PHP.

I am strongly recommend to install and configure memcache for best performance. 
PressFlow is not required replacement for standard Drupal 7 core (but for Drupal 6 is).

Also sites/default/files folder must be mounted from S3 bucket (read here how to manage it https://sites.google.com/site/truthkos/home/tutorials/amazon-web-services/working-with-ec2-instances/setup-a-s3-connection-to-ec2-instance-via-fuse)

For anonymous user Varnish will dramatically increase site performance.