Need a bigger database? Just a few Heroku CLI commands. Bigger web servers? 2 clicks. Want a test database to run queries against? 1 Heroku CLI command. Want to test a branch of your code against the staging database? Automatically done via GitHub PRs, with DNS setup too.
We had 0 downtime in a year due to actual Heroku issues, developers could push code easily (git push), databases were backed up automatically, servers auto-scaled, etc.
I was genuinely amazed at how well it all worked. The amount of operations work was easily 10x less than if we had to run our own infrastructure on AWS due to not just the hosting, but the tooling. Deployment, rollbacks, slave database setup, configuration management, access control, log aggregation, 3rd party integrations and more.
Heroku does have some drawbacks, request queuing is one of them, mostly due to lack of clear docs and information. Even with its flaws it still saves a massive amount of time and money. For nearly all startups to medium sized companies I'd highly recommend using Heroku.