Heroku seems to be like a more useful Google App Engine, a good place to host a blog or experimental project if you're not into dev-ops.
If you have a knack (at all) for dev-ops, you're not saving yourself anything.
The downtime is pretty bleh too. The moment you start doing multi-provider to offset this, you'll end up doing all the dev-ops work you would've had to have done before. Except now, you have to do it all at once in a time of what is probably high stress.
If you do the dev-ops/automation yourself from the start, you can start small/simple and grow that as you go, deploying your services to arbitrary hosting providers (EC2, Linode, dedicated boxes, whatever).
This is why whenever anybody asks me my opinion of Heroku, I respond, "it's a great place to host that blog engine you wrote in Haskell/Clojure/{hipster_language_of_choice}".