Malcolm,

Here's a couple of examples: http://www.geocities.com/df_foxpro/sim2descrord.html has the nodes all displayed in name order which causes tons of crossed lines.

http://www.geocities.com/df_foxpro/sim2.html is after I ran some code to move nodes around in order to reduce the crossings.

The first two (rough cut) diagram interactions are mousing over a connection line alters it's color so you can more easily trace it. If you click a connection line it dims the two endpoint nodes.