Here is a suggestion. Upgrade and if the upgrade is poor then simply downgrade. That way you can decide for yourself if the performance improves, remains the same, or degrades on your particular network setup. I have noticed no change in performance others have. Links to firmware versions (including older versions) along with a link on how to downgrade can be found at the following link.
http://community.wd.com/t/wd-my-cloud-v4-x-and-v2-x-firmware-versions-download-links/148533
