Basically what should someone know as an Entry Level, Mid-level, and Senior Developer working with Rails?

Entry Level

• Create and setup a Rails environment
• Use generators to create models, controllers and migrations
• Create and use a migration to manage the database
• Create a unit test using rspec/etc
• Create a model and basic validations
• Handle a GET request using a Controller, Model, and View
• Handle a POST request using a Controller, Model, and View
• Basic HTML, CSS and JavaScript
• Basic GIT - clone, commit, push

Mid-Level

• Setup and deploy a Rails App for production
• Understand the Rails stack - callbacks, filters, plugins, engines, gems, rack
• Understand and use Active Record associations
• Understand and use scopes to define model abstractions
• Define tests using Cucumber and rSpec
• Understand and use Object Orientation
• Understand and use Design Patterns (explain what they are, know some basic patterns)

Senior-Level

• Analyse and profile an application for performance and memory issues
• Analyses and profile an application for security issues
• Understand database modeling and query analysis
• Tune a production deployment (Passenger, Thin, Apache etc)
• Understand and use Ruby metaprogramming
• Mentoring skills
• Communication skills
• Planning and Estimation