proposal

ActiveSupport::Concern is a feature of Rails that people hold strong
opinions about. In this talk we'll learn what ActiveSupport::Concern gives us 
when included in Rails models and controllers. We'll look at some example code
and discuss the best way to use concerns and test them with RSpec. We'll also
talk about some of the drawbacks and why some developers choose to stay away,
and explore some possible alternatives.

what ActiveSupport::Concern gives us when included in Rails models and controllers

A little awkward. Here's a potential re-write:

how to use ActiveSupport::Concern in Rails model and controller code

(though it might not express the same point.)

Drop the word "possible" in the last sentence; it doesn't carry its weight.

Do you have a title for this?

No title yet, suggestions welcome!

ActiveSupport::Concern is a feature of Rails that people hold strong opinions about.

What opinions? I want the rest of the proposal to follow up on that, but it doesn't really. I think this sentence can go.

We'll, discuss, talk about is this interactive?

Titles:

• Concerning concerns
• I'm concerned about your Rails code.
• This concerns you.

I want to know more about how this talk will help me. Will you tell me when to use concerns? Will you tell me that concerns are all awful? Will you show me features implemented using concerns and without?

Can we also talk about what the difference is between a concern and a mixin/module?