For every mode? Cool! Thank you very much.
And anything I should really know? I wasn't on about a year or two.. lol
Every mode except Easy. As before, Easy Mode is limited to level 30. ( As tiamat already pointed out)
While we're on the topic of levels, new 60+ armor pieces cannot be worn by NM, though they can be worn by HM as well as UM, and they have 6 slots.
Significant changes to skills has been applied to all classes, you would definitely want to find out more information about that from the respective help section for the classes you play.
There are also level 7 stat (primary and secondary) lapises now, they come from a quest in the new content.
I won't mention economy or inflation, I'm sure someone else will tell you how "insane" it has gotten followed by a huge rant ')