It's a great system, but it's different from 3.5 in that the classes are balanced, everyone has powers, and you're required to work together to survive far more than before. A class is defined by its group role and power source, with each class having 2-3 different 'paths' that key off different attributes. Enhancement from gear is now capped off at 20%, and equipment is now given a numerical value and level so the GM knows if its appropriate for the group or not. Monsters have more hit points, are arraigned by types, and default into a group. Most every monster has a power or special ability and maneuver.
Many non-combat spells are now rituals and have prerequisite skill levels in healing, religion, and spell-casting.
Combat is faster, the PCs are hardier at low-levels, and there