I’ve updated this site to the new WP 4 and it seemed to go smoothly. It did require a database update, so if you decide to upgrade soon, you may want to be sure you have a backup of your database (though we keep backups of them on the server and can grab them if you have a problem). The new features of WP 4 include some improved editing of both images and content and a new plugin gallery that will make finding and installing plugins easier. Otherwise, it seems much the same as before!
As always, be sure to contact Ryan or I if you have questions or concerns about the upgrading process!