Depends on the use case. If you have a limited budget and a small site, you probably wouldn’t notice much difference. Our one-time install customers generally do well on their own in my experience. I can’t recall any meltdowns or serious problems in the last year with the self-supported instances we’ve set up. (Source: I do all the work for the one-time installs, and I follow up and informally check in with them as I get the digest emails for all these sites over time.)
Upgrading is a one-click affair, but you do have to “push the button” periodically.
I migrated a self installed forum into Discourse hosting. I sent in a .zip of my full backup, and ssl certificate, and it worked out fine. I did add the Discourse team to my setup before making the backup, and and am pretty sure that helped make it easier.
When you’re signing up, be clear what your tolerance for downtime will be, so that the migration can be coordinated accordingly.