In the past (when I was still a solo developer), after being 90% confident the code won't completely break the environment or do something screwy with user data, sticking the code in production and funneling 50% of the requests to it while watching NewRelic.

There are no better user testers than your users, and the risk is only moderate. I could always pull the server down and restore the previous version while trying to fix whatever I broke in the deployment.

But if you aren't doing SaaS, user testing as a solo developer is not really feasible. The best user testing I can think of that doesn't "cost" is a Beta/RC Program for your users to volunteer to get potentially broke software for a discount or just early feature releases. For this to work though, you have to have enough users.