you've already identified the 2 main risks in your post.
* Turnitin don't support the plugin directly - I try to via the forums but if you're looking for full support you'd need to pay me for my time
* The plugin is planned for deprecation with a new plugin that Turnitin are developing themselves to replace my plugin.
The only other thing I could possibly add is that my plugin was not originally designed to work with the other Turnitin products like grademark/writecycle etc - so you might find various things you don't like - such as the fact that the dates in Moodle for start/end of an assignment won't always match the start/end date listed within Turnitin for that same assignment - that isn't usually a problem unless you let your students/teachers interact directly with the turnitin site to use their other tools like grademark etc.
hope that helps.