Shown here is one of the Ranger's three trees (not finalized), and as you can see a lot of points have already been invested. The green boxes indicate skills that have been learned, and as you progress through the tree the downward arrows open up additional branches.
Characters will still learn a base set of spells/abilities, but investing points in the skill trees will allow them to learn additional unique abilities as well. You'll earn one skill point for each level, and all in all you'll probably be able to fill up about 35% of the three trees. That means that there are a lot of decisions to make about how you'd like to customize and play your class.
These aren't mockups, these are screenshots of the system actually up and running in the game. There is still a lot of testing to be done, but this new system will hopefully be released on the live servers by the end of the month.
There are more screenshots and tidbits of information to come. Soldiers and Merchants in particular have some surprises on the way, so I'll be sure to elaborate on those soon ;)