Initially, it won't speed you up. Developing the right provisioning formula requires some investment of time but I think it's time you get back many times over because you don't need to follow a bunch of manual steps and making changes to the infrastructure is easier when it's all code. I prefer chef simply because it's easy to develop customizations; the DSL is just ruby. I have a pretty non-standard application stack but automating the provisioning is pretty straight forward. I can bring up the whole thing from bare machine images in minutes. Check out http://wiki.opscode.com/display/chef/Launch+Cloud+Instances+...

I don't know if there's a puppet equivalent to chef-solo but using it with vagrant and VirtualBox is my favorite way to develop chef recipes. I did short presentation about this a few months ago, see https://docs.google.com/present/edit?id=0AVIsoyl05MRmZGNwY2N...

BTW, the OP talks about needing a separate security group for the puppets but last I checked, the default security group on EC2 makes the machines you own visible to each other and nobody else's that you haven't explicitly permitted. So I think all of that was unnecessary.