But in general, I agree that it has not been a very smooth experience. Having messed around with maddy and mox, Stalwart has had quite a few gotchas. Despite being a single binary promising simplicity, I'm finding it to be a real challenge figuring out how it all fits together, and I'm mostly learning by trial and error since the documentation is often outdated.
My biggest gripe is that it doesn't use the config.toml for every setting, or at least doesn't seem to have the option to do so. I broke my installation and had to find the posgresql key-value pairs for the settings, which was made harder by the fact that everything was stored as binary, which also made me have to edit it as binary as well. These were very simple settings that would have been a breeze in a flat configuration file. I absolutely do not like how necessary the WebAdmin is to manage simple things.
That said, the integration with calendar/contacts is nice even without JMAP... Getting Thunderbird and Roundcube setup with plugins and proper settings made it so easy to get several users setup with calendars, contacts, and shared email-boxes and shared contacts right upon first login.
The S3 storage is also working great (Hetzner Frankfurt VPS paired with AWS eu-central-1), and AWS downtime a few days ago notwithstanding, I'm feeling good about the reliability that gives me, leaving me mainly with the PosgresQL data store the main thing to keep backed up.
This is a hugely ambitious software and as such, there will be many things that I will have a hard time getting used to as a hobbyist, but also a lot to be gained. I'm sticking around for now and waiting for version 1, improved documentation, and more clarity on how it all works.