render from model in Rails 3

mymodel.rb

# yes, sometimes you need to do this. you get pilloried in a forum if you
# ask about it, though!

# this code taken from
# http://wholemeal.co.nz/blog/2011/04/05/rendering-from-a-model-in-rails-3/

class MyModel < ActiveRecord::Base
  # Use the my_models/_my_model.txt.erb view to render this object as a string
  def to_s
    ActionView::Base.new(Rails.configuration.paths.app.views.first).render(
      :partial => 'my_models/my_model', :format => :txt,
      :locals => { :my_model => self}
    )
  end
end

Excellent! Thank you!
I wonder, though, how fast is this, since we know that rails rendering a view can be slow.
Is there a way to embed this model rendering via helper?