You will indeed have to re-implement stuff Rails gives you. But more importantly, you will have to maintain it.<p>I maintain a large-ish Sinatra app that should&#x27;ve been done with Rails. Update cycles on the gems are a nightmare. It feels cobbled together.  it&#x27;s a &quot;half baked homegrown version of Rails.&quot;<p>Someday I will just move the logic to a new Rails app and be done with it. It was a terrible idea.<p>* your experience may vary. :)