It has been almost four months since we released Matomo (Piwik) 3. The major new release came with a new UI, performance and security improvements. If you are still on Matomo 2, the security improvements alone should be worth updating your Matomo now to Matomo 3. We cannot recommend this enough.
Since the Matomo (Piwik) 3.0 release we have released three new versions that fix over 250 issues including more performance and security issues. And new features: the Life Time Revenue, or the Cross Domain linking feature to track visitors across different domains accurately. Also, most plugins from the Matomo Marketplace are now compatible with Matomo 3 so there is no reason to wait anymore.
The update to Matomo (Piwik) 3 should be smooth, but may take a while depending on the amount of data you have. If you have any problem with the update, feel free to get in touch with us. At Matomo and at InnoCraft, the company of the makers of Matomo, we have successfully updated many Matomo installations.