I just upgraded my Android Studio from 3.7 to 4.0. After upgrading, I changed the gradle dependency to 0.7.+ as indicated in the release notes. Now, the IDE is stuck with a background task that says it is "Refreshing" my project. I cannot run the project or do anything as those gets queued behind this task.
Note: it did a maven central update of about 100 MB before which completed successfully.