RuneScape 3 isn't just about a graphical overhaul, although it would be sad to dismiss its visual improvements. The new version includes a customizable interface, six hours of new music, and lots of technical improvements.
Jagex is kicking off RuneScape 3 with the Battle of Lumbridge and the Sixth Age, so get in and start kicking butt from minute one! This event will take place over the span of two months, during which players can ally with a faction and collect divine tears to contribute to their side's ranking. The studio recommends that players experience it with the Java client and not the still-in-testing HTML5 version.
The team's also posted a comprehensive FAQ if you have any specific questions about the changes.