Autoroute is great for use at home, but on the road it is very much a very poor sub for sat/nav.
If you have a passenger, or an empty seat that's got room for a laptop computer, autoroute works well with a GPS attached, with one [rant] caveat. Microsoft call it Autoroute 2005, but the map is horribly out of date in some important areas, (like the new toll M6 section is still missing) and Ireland looks like it's a part of the Gobi desert outside of Urban Dublin![/rant]
Other than the point above, Autoroute with a coupled, (therefore cheap) serial or USB GPS is a useful solution, and a large screen can be very useful in the urban areas. I've used the same concept in Orlando, around Florida and in Denver/Colorado using Delorme's street Atlas, and it has saved a load of hassles on several complex trips.
And before I get shouted at, I've no connections with Microsoft or Delorme.