Chuck, they work fine. BJ (BobJ3) is the late friend and forum member Brian was talking about. BJ used them all the time and highly recommended them. I got a set just to try them and had no problems with them.
The only difficult to work with plastic guide bushings I know of are the old Craftsman style. They have a very thin neck so you need to be careful to not push them too hard against the template or you end up trimming the plastic.
"Living in the D" (this means Detroit!)
"It's fine to disagree with other members as long as you respect their opinions"