I’m on programming.dev and using boost and have only had a couple issues.
Occasional downtime.
I had a weird one where I had someone else’s subscriptions and it gave a wrong user error every time I commented.
As for the apps. Unless they specifically code it to detect and handle the version it’s going to break. Changes to the required input or the output between versions are going to break apps.
That’s kind of the price you pay for running as a collection of instances and not a single one.
Overall it’s been great. But it do keep an account on lemmy.world incase my one goes down.