We have also noticed a big slowdown with the trace on in some of our more complicated models,
One example is an old listed building with lots of different FFL's, we have about 15 stories, some are just there for reference on sections/elevations, however this wreaks havoc with walls showing on the stories you want them to!
One way that does seem to speed this up for us is to trace the project map instead of a view-set from the view map. Obviously this isn't always an option depending on different styles of drawing between practices, this does work for us though.
