I use com.android.tools.build:gradle:2.0.0-alpha3 and gradle 2.8 before I update to Android Studio 2.0 preview 5. It works fine.
After I update to 2.0 preview 5,it tells me to update to com.android.tools.build:gradle:2.0.0-alpha5 and gradle 2.10.
I can't build and run my app normally now. It always uses a old copy of my code though I have changed the code and costs more time to build.
If I turn back to com.android.tools.build:gradle:2.0.0-alpha3 and gradle 2.8.It become right.
Android Studio Version (http://tools.android.com/recent)
Android Gradle Plugin Version (http://tools.android.com/tech-docs/new-build-system)
Android Studio Preview 6 was posted on Jan 21, 2016. Android Studio Preview 7 was posted on Jan 23, 2016.
You can see that the Android Studio Preview updates frequently. If you don't want to deal all kinds of bugs, you would better to use a stable version.
If you want to use more features, you should always keep latest version to avoid bugs.