I've been toying around with the talent calculator a bit trying to come up with a decent spec to finish leveling to 70 with before WOTLK. My Lock is currently 62 and I've been using a FG spec.
I've come up with this build however http://wotlk.wowhead.com/?talent=IdxrbZ0gIzsg0Acsg as it's looking like the Voidwalker is much improved and will be able to hold aggro amazingly well. Just dot the mob up and life tap/drain life.