Joplin Cloud has been out of beta for a few weeks now and since then it has been quietly running without any troubles. There is no known bugs and the service is running smoothly so it's now safe to say that it is production ready!
As a reminder, Joplin Cloud is meant to provide a more seamless Joplin experience - if you want to quickly get started, it's as easy as downloading the app and getting a Joplin Cloud account. Besides improved sync performance, that will give you the ability to collaborate on notebooks with others, as well as publishing and sharing notes.
Of course Joplin still supports other sync options such as Nextcloud, Dropbox and OneDrive or AWS S3. You can also self host using Joplin Server. The advantage of Joplin Cloud being that you don't need to maintain a server yourself - for a small fee you'll get that taken care of.
Additionally, subscribing to Joplin Cloud is a great way to support the project as a whole, including the open source applications. Such support is needed in the long term to provide bug and security fixes, add new features, and provide support.
At some level it is also an experiment, to see if such a service is financially viable and can allow me to work full time on the project. This is certainly something I would like, and perhaps Joplin Cloud combined with your donations will allow that.