It’s definitely worth a look, especially if you’re running in a complex environment, where new closures will be large and unwieldy. It’s very easy, too. Any time you use:

def note(text, options = {}, &block)
  options[:class] = ((options[:class] || "") + " form-note").strip
  content_tag(:div, text, options, &block)
end

Instead, don’t explicitly name the block parameter; just yield to it, and you prevent all the messiness of creating a new Proc object.

def note(text, options = {})
  options[:class] = ((options[:class] || "") + " form-note").strip
  content_tag(:div, text, options) {|*block_args| yield(*block_args) if block_given? }
end

I don’t have benchmarks just yet, but anecdotally it has definitely slowed instance memory consumption in my apps. It’s worth taking a look at!