One thing I never found out is, once you choose are you stuck with it? and if not, when I change do I loose active/passive skills from the other 'destiny'? And are the bonuses (increased skill training for example) based on a skill you rank or automatic once you choose one?
The answers to those questions pretty much determine if I bother logging on again.
You're not stuck with it. Every rebirth, you can change it, including free rebirths. And after the revision that changed it from what it was to what it is now, there are no restrictions, just boosted stat gain and improved skill training for skills relating to each class.