It sticks with the cartoony visuals despite the upgrades and features voice chat and a new coaching system for newbs to get tutored by DotA veterans.
Defence of the Ancients is a mod or 'custom scenario' for Blizzard's Warcraft III: Reign of Chaos, with developer IceFrog appointed as the custodian for the still running community made game. Valve has IceFrog lending assistance with DotA 2.
Defence of the Ancients 2 releases on PC and Mac next year. Excited?