Unleash the Fury
This is probably the coolest feature of an MMO that I've seen in a long time,
"A gripe heard often in MMOs are the inability of late adopters to play with early adopters of a game as their friends have far outranked them. In Unleash the Fury, higher ranking skills do not replace the lower ranks in your spell book and this allows and encourages more experienced players to play with less experienced ones by selecting matching skills."
if put together well with what they say about their hotbar templates and grouping, this could be very cool.
There are also few other realy neat ideas in there too.