Hi,
1) The values should be in milliseconds.
2) In 2.53 the viz.intersect() command is pretty much your only option. You might be able to speed up the call by disabling collisions with objects that you are not interested in.
Code:
object.disable(viz.COLLISION)
Another thing you can do is create very low-res versions of your models. These low-res versions will represent the collision mesh of the high-res models. Then disable collisions on the high-res and disable rendering on the low-res. The viz.intersect() command performs the intersection on each triangle in your model, regardless of the collision shape you defined for it using the collide*() functions.
Vizard 3.0 allows you to use the underlying physics engine to perform intersection tests, which will be optimized for the collision shapes defined for each model. I just did a test with a simple scene, and performing 100 intersections per frame caused the update time to be 25 ms using viz.intersect() and 2.5 ms using the physics line intersect command.