dev10 is a major release, courtesy of the new compiler plugin. Make sure that when you upgrade to dev10 that you also set kotlinCompilerVersion to 1.3.70-dev-withExperimentalGoogleExtensions-20200424 in your composeOptions in your module’s Gradle script.
As the name suggests, this plugin is based on Kotlin 1.3.70. There have been reports of some hiccups in using newer Kotlin builds with this plugin, so if you get strange results, try setting your org.jetbrains.kotlin:kotlin-gradle-plugin version in your top-level Gradle script to 1.3.70 to match the plugin version.
However, on the positive side, there are reports that you can now use kapt-based libraries like Room in a Compose module. Previously, you need to keep those separate, due to conflicts between the annotation processors and the Compose compiler plugin. And, there are reports that coroutines are working a lot better, though there may still be some lingering issues with using Flow.
All in all, it is well worth trying to move to dev10 soon, and major thanks go out to the entire Compose development team for the updates!