absolutely, cable tray and conduits would be very helpful. I spend hours tying to built cable tray from scratch. it still doesn't work. i know AutoCAD mep2008 has 3d cable tray and coduits. i would be nice if i can import those to revit mep.
A must have indeed. Right now our electrical guys use duct and pipe for cable tray and conduit and it makes it harder for us to differ what is actually duct and pipe if someone isn't using the right types.