
We just had a discussion about this in the "Vectors, vertices and a geek" thread. It wasn't originally about this, but it turned into that.
First, in my code, I use the equation
fPointDistance = vPoint .Dot (vPlaneNormal)  vPlaneDistance;
If fPointDistance is negative, then the point is behind.
Mathematically, the dot product is only for vectors, not vertices. However, as long as you have a well defined conversion between vectors and vertices and visa versa, then you can use vertices where vectors are used. 99.999999999% of all people take advantage of the implicit conversion between vertices and vectors (i.e. vector (i,j,k) = vertex (i,j,k)).
In other words, don't worry about using vertices in place of vectors.
Tim
