That ‘s exiting to welcome WordPress 4.0 after many times upgrade. This ‘s really a perfect version what we can believe it ‘s stable and nice enough for our purpose use on desktop and mobile device. If you still doubt about what it can bring to us, you can check this video
After updating you will see this line
Thank you for updating! WordPress 4.0 brings you a smoother writing and management experience.
Yes, it ‘s really nice for our world! Thanks WordPress team.