There has been a lot of discussion on these and the Chaos Group forums as to whether or not Digimation's SpeedTree plugin can be used in V-Ray.
They can.
You just have to go through a little workaround to get them looking good.
So here it is.
Tutorial: SpeedTree in V-Ray!
Yay! WOOO!
Also, a plug for myself. Check out
Sweaty Robot.