Hi,
Think of it as a "gamma" release. the one after the last Beta, but before the general release.
As a result, the core functionality is fine, however, there are some features that are not finished, and some of the content for the final release isn't ready (though it is trickling through).
If you're planning on creating routes or content (including rollingstock) in TS19, using all the visual enhancements, it's fine.
It's frustrating for some, because a number of routes are to be included, but aren't yet ready.
As you can see from philskene's videos, he seem to be enjoying the updates to his routes!
Colin