A host of new features have been added which can be enjoyed by new players and high level characters alike. You can align yourself with a god, and can obtain special abilities and other perks through acts of worship . The addition of new class-specific abilities also gives you new choices as you progress, and gives level 70 players something new to work toward.
The expansion also adds Tinkering, which allows you to make new items, and Transmuting, which allows you to add additional features to existing items. The downside is that these are both "sub" tradeskills, and how far you can advance in them is determined by what level your traditional tradeskill ability is. If you only want to be a top-notch Tinker or Transmuter without learning another tradeskill first, you're out of luck.
[Ed. note: this last gripe has since been changed. According to Senior Producer Scott Hartsman, "the new Secondary tradeskills will use either the highest of your Adventure Level or Tradeskill Level to determine how far you can progress. So a Level 70 Berserker, with no other tradeskills at all, would be able to advance to 350 Tinkering or Transmuting]