Gamespot is the latest to post its hands-on preview of Borderlands. The article delves a bit into the skill tree of two of the characters and accompanying are a few tasty screenshots.
Sirens, on the other hand, have the "phasewalk" ability, which shifts them in and out of this dimension, essentially cloaking them for a few moments. Phasewalking also gives you a short speed boost and the ability to perform powerful melee attacks and cause damage to nearby enemies when shifting. Because special abilities have a cooldown time, it seems best to save your character's special powers for when you really need them. Like the soldier, the siren can also learn additional skill trees. In this case, the controller, elemental, and assassin paths help you regenerate health or daze enemies; add elemental damage, such as fire or corrosion, to your attacks; and increase your melee or critical hit damage, respectively. While you gain upgrade points by earning experience levels, you won't be able gain enough points to max out every single skill tree in any single play-through, so you'll want to choose those skills that best fit your own playing style.