In case anyone is curious, here's the list of changes according to the forum software developer:

Primary changes in this release:
• Every forum page has been updated to be Mobile Friendly
• Completely updated Control Panel pages
• Updated Control Panel to include inline documentation and entry examples.
• SEO Friendly URLs
• Drag-drop Attachment Manager
• Proper Timezones and automatic Daylight Saving Time adjustments
• New Login pages
• Updated Voting / Polls
• Image preview in the Attachment Manger
• Entire User Profile editor within the Control Panel's Member Editor.
• Updated User Settings and Preferences pages
• Who's Online -- Major updates. reduce each item to a single row.
• Profile Page, with social networking support
• Updated to accept HTTPS in addition to HTTP
• Everything is now IPv6 compatible.
• Proxy support
• UBB Gallery pages have been rewritten
• Complete overhaul for the Language files.
• Support for CDNs and Proxy Detection for parsing spammers and checking them against StopForumSpam
• Updated all pages to validate as error free HTML5 pages with CSS3
• Cleanup and optimization of all HTML, CSS, and PHP code.
• Putting the "Threads" back in to UBB.threads